diff --git a/app/api/documents.py b/app/api/documents.py
index d786ee9..c8d2de9 100644
--- a/app/api/documents.py
+++ b/app/api/documents.py
@@ -402,7 +402,7 @@ async def upload_document(
     library_path: str | None = Form(None, description="자료실 경로 (자동 @library/ 태깅)"),
 ):
     """파일 업로드 → Inbox 저장 + DB 등록 + 처리 큐 등록"""
-    from core.library import LIBRARY_PREFIX, normalize_library_path
+    from core.library import DEFAULT_LIBRARY_PATH, LIBRARY_PREFIX, normalize_library_path
 
     # doc_purpose 검증
     if doc_purpose is not None:
@@ -421,6 +421,10 @@ async def upload_document(
         except ValueError as e:
             raise HTTPException(status_code=400, detail=f"잘못된 자료실 경로: {e}")
 
+    # 자료실 업로드인데 경로 미지정 → 미분류 자동 태깅
+    if doc_purpose == "business" and not library_tag:
+        library_tag = f"{LIBRARY_PREFIX}{DEFAULT_LIBRARY_PATH}"
+
     if not file.filename:
         raise HTTPException(status_code=400, detail="파일명이 필요합니다")
 
diff --git a/app/core/library.py b/app/core/library.py
index 5d32dda..19be47b 100644
--- a/app/core/library.py
+++ b/app/core/library.py
@@ -4,6 +4,7 @@ user_tags 내 @library/ 접두사 태그를 정규화·검증·추출한다.
 """
 
 LIBRARY_PREFIX = "@library/"
+DEFAULT_LIBRARY_PATH = "미분류"
 MAX_DEPTH = 5
 MAX_SEGMENT_LEN = 30
 
diff --git a/frontend/src/routes/library/+page.svelte b/frontend/src/routes/library/+page.svelte
index bdb6063..afd35a9 100644
--- a/frontend/src/routes/library/+page.svelte
+++ b/frontend/src/routes/library/+page.svelte
@@ -42,6 +42,7 @@
   ];
 
   const ODF_FORMATS = ['ods', 'odt', 'odp', 'odoc', 'osheet'];
+  const DEFAULT_LIBRARY_PATH = '미분류';
 
   // ─── 데이터 로드 ───
 
@@ -198,7 +199,7 @@
       const formData = new FormData();
       formData.append('file', file);
       formData.append('doc_purpose', 'business');
-      if (activePath) formData.append('library_path', activePath);
+      formData.append('library_path', activePath || DEFAULT_LIBRARY_PATH);
       try {
         await api('/documents/', { method: 'POST', body: formData });
         success++;