diff --git a/migrations/115_doc_purpose.sql b/migrations/115_doc_purpose.sql
index 790369b..e7994ba 100644
--- a/migrations/115_doc_purpose.sql
+++ b/migrations/115_doc_purpose.sql
@@ -1,5 +1,10 @@
 -- 문서 용도 구분: business(업무용) | knowledge(참조용)
--- 기존 문서는 NULL → AI 재분류 시 점진 채움
--- 우선순위: 수동 수정 > 업로드 시 명시값 > AI 추론
-CREATE TYPE document_purpose AS ENUM ('business', 'knowledge');
-ALTER TABLE documents ADD COLUMN doc_purpose document_purpose;
+DO $$
+BEGIN
+  IF NOT EXISTS (SELECT 1 FROM pg_type WHERE typname = 'document_purpose') THEN
+    CREATE TYPE document_purpose AS ENUM ('business', 'knowledge');
+  END IF;
+  IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name='documents' AND column_name='doc_purpose') THEN
+    ALTER TABLE documents ADD COLUMN doc_purpose document_purpose;
+  END IF;
+END $$;