Provided is an operation device (10) to be held by a user with one hand when used. The operation device (10) includes: a recessed portion (14) formed at a position at which at least one of a thumb and fingers is placed when the user holds the operation device (10) ; and a main button (13) which is disposed at a bottom of the recessed portion (14) and has a top surface adjacent to a rim portion (14a) forming a side surface of the recessed portion (14).
