diff --git a/app/Services/DocumentService.php b/app/Services/DocumentService.php
new file mode 100644
index 0000000..e52df08
--- /dev/null
+++ b/app/Services/DocumentService.php
@@ -0,0 +1,524 @@
+<?php
+
+namespace App\Services;
+
+use App\Models\Documents\Document;
+use App\Models\Documents\DocumentApproval;
+use App\Models\Documents\DocumentAttachment;
+use App\Models\Documents\DocumentData;
+use Illuminate\Contracts\Pagination\LengthAwarePaginator;
+use Illuminate\Support\Facades\DB;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+
+class DocumentService extends Service
+{
+    // =========================================================================
+    // 문서 목록/상세
+    // =========================================================================
+
+    /**
+     * 문서 목록 조회
+     */
+    public function list(array $params): LengthAwarePaginator
+    {
+        $tenantId = $this->tenantId();
+
+        $query = Document::query()
+            ->where('tenant_id', $tenantId)
+            ->with([
+                'template:id,name,category',
+                'creator:id,name',
+            ]);
+
+        // 상태 필터
+        if (! empty($params['status'])) {
+            $query->where('status', $params['status']);
+        }
+
+        // 템플릿 필터
+        if (! empty($params['template_id'])) {
+            $query->where('template_id', $params['template_id']);
+        }
+
+        // 검색 (문서번호, 제목)
+        if (! empty($params['search'])) {
+            $search = $params['search'];
+            $query->where(function ($q) use ($search) {
+                $q->where('document_no', 'like', "%{$search}%")
+                    ->orWhere('title', 'like', "%{$search}%");
+            });
+        }
+
+        // 날짜 범위 필터
+        if (! empty($params['from_date'])) {
+            $query->whereDate('created_at', '>=', $params['from_date']);
+        }
+        if (! empty($params['to_date'])) {
+            $query->whereDate('created_at', '<=', $params['to_date']);
+        }
+
+        // 정렬
+        $sortBy = $params['sort_by'] ?? 'created_at';
+        $sortDir = $params['sort_dir'] ?? 'desc';
+        $query->orderBy($sortBy, $sortDir);
+
+        $perPage = $params['per_page'] ?? 20;
+
+        return $query->paginate($perPage);
+    }
+
+    /**
+     * 문서 상세 조회
+     */
+    public function show(int $id): Document
+    {
+        $tenantId = $this->tenantId();
+
+        return Document::query()
+            ->where('tenant_id', $tenantId)
+            ->with([
+                'template:id,name,category,title',
+                'template.approvalLines',
+                'template.basicFields',
+                'template.sections.items',
+                'template.columns',
+                'approvals.user:id,name',
+                'data',
+                'attachments.file',
+                'creator:id,name',
+                'updater:id,name',
+            ])
+            ->findOrFail($id);
+    }
+
+    // =========================================================================
+    // 문서 생성/수정/삭제
+    // =========================================================================
+
+    /**
+     * 문서 생성
+     */
+    public function create(array $data): Document
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($data, $tenantId, $userId) {
+            // 문서번호 생성
+            $documentNo = $this->generateDocumentNo($tenantId, $data['template_id']);
+
+            // 문서 생성
+            $document = Document::create([
+                'tenant_id' => $tenantId,
+                'template_id' => $data['template_id'],
+                'document_no' => $documentNo,
+                'title' => $data['title'],
+                'status' => Document::STATUS_DRAFT,
+                'linkable_type' => $data['linkable_type'] ?? null,
+                'linkable_id' => $data['linkable_id'] ?? null,
+                'created_by' => $userId,
+                'updated_by' => $userId,
+            ]);
+
+            // 결재선 생성
+            if (! empty($data['approvers'])) {
+                $this->createApprovals($document, $data['approvers'], $userId);
+            }
+
+            // 문서 데이터 저장
+            if (! empty($data['data'])) {
+                $this->saveDocumentData($document, $data['data']);
+            }
+
+            // 첨부파일 연결
+            if (! empty($data['attachments'])) {
+                $this->attachFiles($document, $data['attachments'], $userId);
+            }
+
+            return $document->fresh([
+                'template:id,name,category',
+                'approvals.user:id,name',
+                'data',
+                'attachments.file',
+                'creator:id,name',
+            ]);
+        });
+    }
+
+    /**
+     * 문서 수정
+     */
+    public function update(int $id, array $data): Document
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($id, $data, $tenantId, $userId) {
+            $document = Document::query()
+                ->where('tenant_id', $tenantId)
+                ->findOrFail($id);
+
+            // 수정 가능 상태 확인
+            if (! $document->canEdit()) {
+                throw new BadRequestHttpException(__('error.document.not_editable'));
+            }
+
+            // 기본 정보 수정
+            $document->fill([
+                'title' => $data['title'] ?? $document->title,
+                'linkable_type' => $data['linkable_type'] ?? $document->linkable_type,
+                'linkable_id' => $data['linkable_id'] ?? $document->linkable_id,
+                'updated_by' => $userId,
+            ]);
+
+            // 반려 상태에서 수정 시 DRAFT로 변경
+            if ($document->status === Document::STATUS_REJECTED) {
+                $document->status = Document::STATUS_DRAFT;
+                $document->submitted_at = null;
+                $document->completed_at = null;
+            }
+
+            $document->save();
+
+            // 결재선 수정
+            if (isset($data['approvers'])) {
+                $document->approvals()->delete();
+                if (! empty($data['approvers'])) {
+                    $this->createApprovals($document, $data['approvers'], $userId);
+                }
+            }
+
+            // 문서 데이터 수정
+            if (isset($data['data'])) {
+                $document->data()->delete();
+                if (! empty($data['data'])) {
+                    $this->saveDocumentData($document, $data['data']);
+                }
+            }
+
+            // 첨부파일 수정
+            if (isset($data['attachments'])) {
+                $document->attachments()->delete();
+                if (! empty($data['attachments'])) {
+                    $this->attachFiles($document, $data['attachments'], $userId);
+                }
+            }
+
+            return $document->fresh([
+                'template:id,name,category',
+                'approvals.user:id,name',
+                'data',
+                'attachments.file',
+                'creator:id,name',
+            ]);
+        });
+    }
+
+    /**
+     * 문서 삭제
+     */
+    public function destroy(int $id): bool
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($id, $tenantId, $userId) {
+            $document = Document::query()
+                ->where('tenant_id', $tenantId)
+                ->findOrFail($id);
+
+            // DRAFT 상태만 삭제 가능
+            if ($document->status !== Document::STATUS_DRAFT) {
+                throw new BadRequestHttpException(__('error.document.not_deletable'));
+            }
+
+            $document->deleted_by = $userId;
+            $document->save();
+            $document->delete();
+
+            return true;
+        });
+    }
+
+    // =========================================================================
+    // 결재 처리
+    // =========================================================================
+
+    /**
+     * 결재 요청 (DRAFT → PENDING)
+     */
+    public function submit(int $id): Document
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($id, $tenantId, $userId) {
+            $document = Document::query()
+                ->where('tenant_id', $tenantId)
+                ->findOrFail($id);
+
+            // 결재 요청 가능 상태 확인
+            if (! $document->canSubmit()) {
+                throw new BadRequestHttpException(__('error.document.not_submittable'));
+            }
+
+            // 결재선 존재 확인
+            $approvalCount = $document->approvals()->count();
+            if ($approvalCount === 0) {
+                throw new BadRequestHttpException(__('error.document.approvers_required'));
+            }
+
+            $document->status = Document::STATUS_PENDING;
+            $document->submitted_at = now();
+            $document->updated_by = $userId;
+            $document->save();
+
+            return $document->fresh([
+                'template:id,name,category',
+                'approvals.user:id,name',
+                'creator:id,name',
+            ]);
+        });
+    }
+
+    /**
+     * 결재 승인
+     */
+    public function approve(int $id, ?string $comment = null): Document
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($id, $comment, $tenantId, $userId) {
+            $document = Document::query()
+                ->where('tenant_id', $tenantId)
+                ->findOrFail($id);
+
+            // 결재 가능 상태 확인
+            if (! $document->canApprove()) {
+                throw new BadRequestHttpException(__('error.document.not_approvable'));
+            }
+
+            // 현재 사용자의 대기 중인 결재 단계 찾기
+            $myApproval = $document->approvals()
+                ->where('user_id', $userId)
+                ->where('status', DocumentApproval::STATUS_PENDING)
+                ->orderBy('step')
+                ->first();
+
+            if (! $myApproval) {
+                throw new BadRequestHttpException(__('error.document.not_your_turn'));
+            }
+
+            // 순차 결재 확인 (이전 단계가 완료되었는지)
+            $pendingBefore = $document->approvals()
+                ->where('step', '<', $myApproval->step)
+                ->where('status', DocumentApproval::STATUS_PENDING)
+                ->exists();
+
+            if ($pendingBefore) {
+                throw new BadRequestHttpException(__('error.document.not_your_turn'));
+            }
+
+            // 승인 처리
+            $myApproval->status = DocumentApproval::STATUS_APPROVED;
+            $myApproval->comment = $comment;
+            $myApproval->acted_at = now();
+            $myApproval->updated_by = $userId;
+            $myApproval->save();
+
+            // 모든 결재 완료 확인
+            $allApproved = ! $document->approvals()
+                ->where('status', DocumentApproval::STATUS_PENDING)
+                ->exists();
+
+            if ($allApproved) {
+                $document->status = Document::STATUS_APPROVED;
+                $document->completed_at = now();
+            }
+
+            $document->updated_by = $userId;
+            $document->save();
+
+            return $document->fresh([
+                'template:id,name,category',
+                'approvals.user:id,name',
+                'creator:id,name',
+            ]);
+        });
+    }
+
+    /**
+     * 결재 반려
+     */
+    public function reject(int $id, string $comment): Document
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($id, $comment, $tenantId, $userId) {
+            $document = Document::query()
+                ->where('tenant_id', $tenantId)
+                ->findOrFail($id);
+
+            // 결재 가능 상태 확인
+            if (! $document->canApprove()) {
+                throw new BadRequestHttpException(__('error.document.not_approvable'));
+            }
+
+            // 현재 사용자의 대기 중인 결재 단계 찾기
+            $myApproval = $document->approvals()
+                ->where('user_id', $userId)
+                ->where('status', DocumentApproval::STATUS_PENDING)
+                ->orderBy('step')
+                ->first();
+
+            if (! $myApproval) {
+                throw new BadRequestHttpException(__('error.document.not_your_turn'));
+            }
+
+            // 순차 결재 확인
+            $pendingBefore = $document->approvals()
+                ->where('step', '<', $myApproval->step)
+                ->where('status', DocumentApproval::STATUS_PENDING)
+                ->exists();
+
+            if ($pendingBefore) {
+                throw new BadRequestHttpException(__('error.document.not_your_turn'));
+            }
+
+            // 반려 처리
+            $myApproval->status = DocumentApproval::STATUS_REJECTED;
+            $myApproval->comment = $comment;
+            $myApproval->acted_at = now();
+            $myApproval->updated_by = $userId;
+            $myApproval->save();
+
+            // 문서 반려 상태로 변경
+            $document->status = Document::STATUS_REJECTED;
+            $document->completed_at = now();
+            $document->updated_by = $userId;
+            $document->save();
+
+            return $document->fresh([
+                'template:id,name,category',
+                'approvals.user:id,name',
+                'creator:id,name',
+            ]);
+        });
+    }
+
+    /**
+     * 결재 취소/회수 (작성자만)
+     */
+    public function cancel(int $id): Document
+    {
+        $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
+
+        return DB::transaction(function () use ($id, $tenantId, $userId) {
+            $document = Document::query()
+                ->where('tenant_id', $tenantId)
+                ->findOrFail($id);
+
+            // 취소 가능 상태 확인
+            if (! $document->canCancel()) {
+                throw new BadRequestHttpException(__('error.document.not_cancellable'));
+            }
+
+            // 작성자만 취소 가능
+            if ($document->created_by !== $userId) {
+                throw new BadRequestHttpException(__('error.document.only_creator_can_cancel'));
+            }
+
+            $document->status = Document::STATUS_CANCELLED;
+            $document->completed_at = now();
+            $document->updated_by = $userId;
+            $document->save();
+
+            return $document->fresh([
+                'template:id,name,category',
+                'creator:id,name',
+            ]);
+        });
+    }
+
+    // =========================================================================
+    // 헬퍼 메서드
+    // =========================================================================
+
+    /**
+     * 문서번호 생성
+     */
+    private function generateDocumentNo(int $tenantId, int $templateId): string
+    {
+        $prefix = 'DOC';
+        $date = now()->format('Ymd');
+
+        // 오늘 생성된 문서 중 마지막 번호 조회
+        $lastNumber = Document::query()
+            ->where('tenant_id', $tenantId)
+            ->where('document_no', 'like', "{$prefix}-{$date}-%")
+            ->orderByDesc('document_no')
+            ->value('document_no');
+
+        if ($lastNumber) {
+            $sequence = (int) substr($lastNumber, -4) + 1;
+        } else {
+            $sequence = 1;
+        }
+
+        return sprintf('%s-%s-%04d', $prefix, $date, $sequence);
+    }
+
+    /**
+     * 결재선 생성
+     */
+    private function createApprovals(Document $document, array $approvers, int $userId): void
+    {
+        foreach ($approvers as $index => $approver) {
+            DocumentApproval::create([
+                'document_id' => $document->id,
+                'user_id' => $approver['user_id'],
+                'step' => $index + 1,
+                'role' => $approver['role'] ?? '승인',
+                'status' => DocumentApproval::STATUS_PENDING,
+                'created_by' => $userId,
+                'updated_by' => $userId,
+            ]);
+        }
+    }
+
+    /**
+     * 문서 데이터 저장
+     */
+    private function saveDocumentData(Document $document, array $dataItems): void
+    {
+        foreach ($dataItems as $item) {
+            DocumentData::create([
+                'document_id' => $document->id,
+                'section_id' => $item['section_id'] ?? null,
+                'column_id' => $item['column_id'] ?? null,
+                'row_index' => $item['row_index'] ?? 0,
+                'field_key' => $item['field_key'],
+                'field_value' => $item['field_value'] ?? null,
+            ]);
+        }
+    }
+
+    /**
+     * 첨부파일 연결
+     */
+    private function attachFiles(Document $document, array $attachments, int $userId): void
+    {
+        foreach ($attachments as $attachment) {
+            DocumentAttachment::create([
+                'document_id' => $document->id,
+                'file_id' => $attachment['file_id'],
+                'attachment_type' => $attachment['attachment_type'] ?? DocumentAttachment::TYPE_GENERAL,
+                'description' => $attachment['description'] ?? null,
+                'created_by' => $userId,
+            ]);
+        }
+    }
+}