can't judge a book by its cover

You can't judge a book by its cover—her quiet manner hides a very confident leader.

彼女は物静かだが、とても自信のあるリーダーだ。見た目だけでは判断できない。

The restaurant looked plain from outside, but the food was excellent; you can't judge a book by its cover.

そのレストランは外から見ると地味だったが、料理は素晴らしかった。見た目で判断してはいけない。

Don't dismiss him because of his old clothes. You can't judge a book by its cover.

古い服を着ているからといって彼を見下してはいけない。見た目だけでは判断できない。

That small, inexpensive phone is surprisingly powerful. You really can't judge a book by its cover.

その小さくて安価な携帯電話は、驚くほど高性能だ。本当に見た目だけでは判断できない。

I thought the course would be easy, but it was challenging. You can't judge a book by its cover.

その講座は簡単そうだと思ったが、難しかった。見た目だけでは判断できない。