A switch mechanism of a detection sensor unmounted type has a configuration in which an attaching surface for a case body for containing a movable member moved in conjunction with a button operation and a mounting surface for a detection sensor operative to electrically detect a change in the position of the movable member attendant on the button operation are different, and a magnifying mechanism operative to magnifyingly transmit the change in the position of the movable member attendant on the button operation is mounted in the switch mechanism.