diff --git a/app/models/memo.rb b/app/models/memo.rb
index aa0af8a02..30fb80490 100644
--- a/app/models/memo.rb
+++ b/app/models/memo.rb
@@ -188,7 +188,19 @@ class Memo < ApplicationRecord
   end
 
   def update_attachments(attachment_ids)
-    Attachment.where(id: attachment_ids).update_all(container_id: id, container_type: "Memo")
+    if attachment_ids.present?
+      attachment_ids = attachment_ids -[nil] if attachment_ids.is_a? Array
+      old_attachment_uuids = Attachment.where(container_id: id, container_type: "Memo").pluck(:uuid)
+      if old_attachment_uuids.present?
+        del_attachment_uuids = old_attachment_uuids - attachment_ids
+        Attachment.where(uuid: del_attachment_uuids).update_all(container_id: nil, container_type: nil)
+      end
+      if attachment_ids.present?
+        Attachment.where(uuid: attachment_ids).update_all(container_id: id, container_type: "Memo")
+      end
+    else
+      Attachment.where(container_id: id, container_type: "Memo").update_all(container_id: nil, container_type: nil)
+    end
   end
 
 	private