To ensure a push knob to be automatically reset from a pressed position to a projected position, interlocked with the operation of an ignition switch, when the ignition switch is turned off.

A push knob 2 is free to advance and retreat along an area between a projected position A and a pressed position B, and has a cam block 3 and a first spring. Also, a switch body 1 has an actuator 6. This actuator 6 is formed out of a coil 61 to receive exciting current from an ignition switch, an armature 62 attracted to the coil 61, a third spring 63 integrated with the armature 62, and a pin 64 formed on the third spring 63. In this case, the pin 64 parts from a cam groove 41, when the ignition switch is turned off.