To provide a key switch device for simultaneously turning on or off a plurality of microswitches.

A switch mounting main plate 2 is fixed to a rear part of a cylinder lock body, a plurality of microswitches 3 layered in the fore and aft direction are fixed by screws 5 to the switch mounting main plate 2 with a switch mounting sub-plate 4 abutting on them, a cam cylinder 6 for switch operation inserted between the switch mounting main plate 2 and the switch mounting sub-plate 4 is coupled to a rotor, and the plurality of microswitches are turned on/off by the cam cylinder 6 for switch operation.