diff --git a/ecs/jskult-batch/src/batch/mst_inst_all.py b/ecs/jskult-batch/src/batch/mst_inst_all.py
index 33e47faa..d6d9642b 100644
--- a/ecs/jskult-batch/src/batch/mst_inst_all.py
+++ b/ecs/jskult-batch/src/batch/mst_inst_all.py
@@ -135,17 +135,6 @@ class MstInstAll(JskultBatchEntrypoint):
         return
 
     def _insert_mst_inst_all_from_com_inst(self, db: Database):
-        # オプティマイザのderived_mergeフラグをoffにする
-        try:
-            sql = """
-                SET SESSION optimizer_switch = 'derived_merge=off'
-            """
-            db.execute(sql)
-            logger.info("オプティマイザのderived_mergeフラグ = Off")
-        except Exception as e:
-            logger.info("オプティマイザのderived_mergeフラグの値変更に失敗")
-            raise e
-
         # com_instから、mst_inst_allへInsert
         try:
             sql = """