Hello @katsumi.baba,
Welcome to the Dynamo forums! We are super excited to see your first question pop up here and hope that the forums can provide a lot of help in your Dynamo journey 
One quick note - I’ve edited your post to also include the English translation (Sorry if Google Translate doesn’t quite capture it correctly) as this is an English language forum… you’ll quite simply get a lot more help if you ask for help in English! So if possible, please try and post in English (and Google translate is totally fine! It’s the intention more than anything else) and provide good images like you have.
If possible, when you have information passing through a node that is causing an error downstream, please include the Preview bubble (So in this case from the List.GetItemAtIndex node that plugs into the WallType.ByName node) so that the community can better help you
So, to the question at hand. Are you trying to select a Revit wall type by name from an Excel sheet?