To hold a stable ON-state, despite a small quantity of movement of a switch operating member.

In the case that this device 100 is equipped with first and second contact pieces 1, 2 having spring nature and constructed so as to be turned on/off by bringing into contact/setting apart respective contact parts 11, 12 with/from each other of the first and second contact pieces 1, 2, a switch operating mechanism 3 is provided. As a result of this, the two contact parts 11, 12 are caused to make contact with each other by moving the contact part 11 towards the contact part 21 of the second contact piece 2 by deforming the first contact piece 1 so as to turn on the switch device, and along with this, by moving the contact part 21 towards the contact part 11 of the first contact piece 1 by deforming the second contact piece 2.