An electronic device includes a casing having an opening; a circuit board having a plurality of electrodes, which is provided inside the casing; a contact member having a plurality of contact points corresponding to the electrodes, which is provided so as to seal the opening; and a key unit (press-key unit) having a key operation unit corresponding to the contact points, which is provided to the opening. The key unit (press-key unit) is attached to the opening detachably.