diff --git a/app/Http/Controllers/Api/V1/ItemsBomController.php b/app/Http/Controllers/Api/V1/ItemsBomController.php
index de217429..71d3b429 100644
--- a/app/Http/Controllers/Api/V1/ItemsBomController.php
+++ b/app/Http/Controllers/Api/V1/ItemsBomController.php
@@ -446,12 +446,13 @@ private function expandBomItems(array $bom): array
                 'child_item_type' => $childItem?->item_type,
                 'unit' => $childItem?->unit,
                 'quantity' => $entry['quantity'] ?? 1,
+                'category' => $entry['category'] ?? null,
             ];
         })->toArray();
     }
 
     /**
-     * BOM 트리 구조 빌드 (재귀)
+     * BOM 트리 구조 빌드 (재귀, category 필드가 있으면 3단계 그룹화)
      */
     private function buildBomTree(Item $item, int $maxDepth, int $currentDepth): array
     {
@@ -478,14 +479,47 @@ private function buildBomTree(Item $item, int $maxDepth, int $currentDepth): arr
             ->get()
             ->keyBy('id');
 
-        foreach ($bom as $entry) {
-            $childItemId = $entry['child_item_id'] ?? null;
-            $childItem = $childItems[$childItemId] ?? null;
+        // category 필드가 있으면 카테고리별 그룹 노드 생성 (3단계)
+        $hasCategory = collect($bom)->contains(fn ($b) => ! empty($b['category']));
 
-            if ($childItem) {
-                $childTree = $this->buildBomTree($childItem, $maxDepth, $currentDepth + 1);
-                $childTree['quantity'] = $entry['quantity'] ?? 1;
-                $result['children'][] = $childTree;
+        if ($hasCategory) {
+            $grouped = [];
+            foreach ($bom as $entry) {
+                $cat = $entry['category'] ?? '기타';
+                $grouped[$cat][] = $entry;
+            }
+
+            foreach ($grouped as $catName => $catEntries) {
+                $catChildren = [];
+                foreach ($catEntries as $entry) {
+                    $childItem = $childItems[$entry['child_item_id'] ?? null] ?? null;
+                    if ($childItem) {
+                        $childTree = $this->buildBomTree($childItem, $maxDepth, $currentDepth + 2);
+                        $childTree['quantity'] = $entry['quantity'] ?? 1;
+                        $catChildren[] = $childTree;
+                    }
+                }
+                if (! empty($catChildren)) {
+                    $result['children'][] = [
+                        'id' => 0,
+                        'code' => '',
+                        'name' => $catName,
+                        'item_type' => 'CAT',
+                        'unit' => '',
+                        'depth' => $currentDepth + 1,
+                        'count' => count($catChildren),
+                        'children' => $catChildren,
+                    ];
+                }
+            }
+        } else {
+            foreach ($bom as $entry) {
+                $childItem = $childItems[$entry['child_item_id'] ?? null] ?? null;
+                if ($childItem) {
+                    $childTree = $this->buildBomTree($childItem, $maxDepth, $currentDepth + 1);
+                    $childTree['quantity'] = $entry['quantity'] ?? 1;
+                    $result['children'][] = $childTree;
+                }
             }
         }