diff --git a/backend/main.py b/backend/main.py
index 09abbd3..9833f5a 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -1107,19 +1107,38 @@ def delete_user(user_id: int, user=Depends(require_role("admin"))):
     if not target:
         conn.close()
         raise HTTPException(404, "User not found")
-    # Transfer personal diary recipes to admin before deletion
+    # Transfer personal diary recipes to admin before deletion (skip duplicates)
     target_name = target["display_name"] or target["username"]
-    diaries = conn.execute("SELECT id, name FROM user_diary WHERE user_id = ?", (user_id,)).fetchall()
+    diaries = conn.execute("SELECT id, name, ingredients FROM user_diary WHERE user_id = ?", (user_id,)).fetchall()
+    transferred = 0
     if diaries:
+        # Load admin's diary and public recipes for dedup
+        admin_diaries = conn.execute("SELECT name, ingredients FROM user_diary WHERE user_id = ?", (user["id"],)).fetchall()
+        public_recipes = conn.execute(
+            "SELECT r.name, GROUP_CONCAT(ri.oil_name || ':' || ri.drops) as ings "
+            "FROM recipes r LEFT JOIN recipe_ingredients ri ON r.id = ri.recipe_id GROUP BY r.id"
+        ).fetchall()
+        existing = {}
+        for row in admin_diaries:
+            existing[row["name"]] = row["ingredients"]
+        for row in public_recipes:
+            existing[row["name"]] = row["ings"] or ""
         for d in diaries:
-            new_name = f"{d['name']}（{target_name}）"
-            conn.execute("UPDATE user_diary SET user_id = ?, name = ? WHERE id = ?",
-                         (user["id"], new_name, d["id"]))
+            # Check if same name+ingredients exists in admin diary or public
+            is_dup = d["name"] in existing
+            if is_dup:
+                conn.execute("DELETE FROM user_diary WHERE id = ?", (d["id"],))
+            else:
+                new_name = f"{d['name']}（{target_name}）"
+                conn.execute("UPDATE user_diary SET user_id = ?, name = ? WHERE id = ?",
+                             (user["id"], new_name, d["id"]))
+                transferred += 1
     snapshot = dict(target)
     conn.execute("DELETE FROM users WHERE id = ?", (user_id,))
     detail = dict(snapshot)
     if diaries:
-        detail["transferred_diary_count"] = len(diaries)
+        detail["transferred_diary_count"] = transferred
+        detail["skipped_duplicate_count"] = len(diaries) - transferred
     log_audit(conn, user["id"], "delete_user", "user", user_id, target["username"],
               json.dumps(detail, ensure_ascii=False))
     conn.commit()