also: アタッシェケース
noun
attaché case; briefcase
A hard, rectangular case with a handle, often used for carrying documents or a laptop. The word is a direct loan from English/French and is widely understood.
彼はアタッシュケースを手に会議室に入った。
He entered the conference room with an attaché case in hand.
新しいアタッシュケースを買うなら、
If you're buying a new attaché case, a light and sturdy one is best.