An attachment structure for operation panel unit includes an operation panel unit 16 with keys 20a to 20c operated by a user, a main body 2 to which the operation panel unit 16 is attached and an outer covering 6 that is attached to the main body 2 so as to cover the operation panel unit 16. The operation panel unit 16 is attached to the main body 2 in such a way that the operation panel unit 16 can slide with respect to the main body 2, in a direction intersecting an attaching direction of the outer covering 6 to the main body 2. When the outer covering 6 is attached to the main body 2 in a state in which the operation panel unit 16 is attached to the main body 2, sliding of the operation panel unit 16 is restricted.