this problem is fixed around 3hours ago. App Store Sandbox - Resolved Issue https://developer.apple.com/system-status/

https://buy.itunes.apple.com/verifyReceipt is okay. https://sandbox.itunes.apple.com/verifyReceipt is returned 21005 from 3rd of December.

I checked by Jenkins every 10 minutes. I confirmed status code returned 21006 around 9 o'clock JST on today. This problem was solved. :)