diff --git a/app/Http/Controllers/ESign/EsignApiController.php b/app/Http/Controllers/ESign/EsignApiController.php
index 212112ab..56bb3db5 100644
--- a/app/Http/Controllers/ESign/EsignApiController.php
+++ b/app/Http/Controllers/ESign/EsignApiController.php
@@ -54,11 +54,15 @@ public function getStamp(): JsonResponse
     public function uploadStamp(Request $request): JsonResponse
     {
         $request->validate([
-            'stamp_image' => 'required|image|max:5120',
+            'stamp_image_data' => 'required|string',
         ]);
 
         $tenantId = session('selected_tenant_id', 1);
-        $file = $request->file('stamp_image');
+        $imageData = base64_decode($request->input('stamp_image_data'));
+
+        if (!$imageData) {
+            return response()->json(['success' => false, 'message' => '이미지 데이터가 올바르지 않습니다.'], 422);
+        }
 
         $path = "esign/{$tenantId}/stamps/company_stamp.png";
 
@@ -67,7 +71,7 @@ public function uploadStamp(Request $request): JsonResponse
             Storage::disk('local')->delete($path);
         }
 
-        Storage::disk('local')->put($path, file_get_contents($file->getRealPath()));
+        Storage::disk('local')->put($path, $imageData);
 
         TenantSetting::updateOrCreate(
             [
diff --git a/resources/views/esign/dashboard.blade.php b/resources/views/esign/dashboard.blade.php
index 4bd3ec6a..b5c3a756 100644
--- a/resources/views/esign/dashboard.blade.php
+++ b/resources/views/esign/dashboard.blade.php
@@ -388,20 +388,26 @@ className={`px-3 py-1 text-sm rounded ${p === pagination.current_page ? 'bg-blue
     const handleUpload = async (e) => {
         const file = e.target.files[0];
         if (!file) return;
+        if (file.size > 5 * 1024 * 1024) { alert('파일 크기는 5MB 이하여야 합니다.'); return; }
         setUploading(true);
         try {
-            const fd = new FormData();
-            fd.append('stamp_image', file);
+            const base64 = await new Promise((resolve, reject) => {
+                const reader = new FileReader();
+                reader.onload = () => resolve(reader.result.split(',')[1]);
+                reader.onerror = reject;
+                reader.readAsDataURL(file);
+            });
             const res = await fetch('/esign/contracts/stamp', {
                 method: 'POST',
-                headers: { 'Accept': 'application/json', 'X-CSRF-TOKEN': csrfToken },
-                body: fd,
+                headers: { ...getHeaders(), 'Content-Type': 'application/json' },
+                body: JSON.stringify({ stamp_image_data: base64 }),
             });
             const json = await res.json();
             if (json.success) {
                 setStamp(json.data);
             } else {
-                alert(json.message || '업로드에 실패했습니다.');
+                const errMsg = json.errors?.stamp_image_data?.[0] || json.message || '업로드에 실패했습니다.';
+                alert(errMsg);
             }
         } catch (e) { alert('업로드 중 오류가 발생했습니다.'); }
         setUploading(false);