A movable operating member 5 is swingably borne by the base 1, and its distal end is moved upward by allowing its proximal end 5b to be pressed downward. The movable contact 3 is separated from the stationary contact 2 upward by moving the distal end of the movable operating member 5 upward. The proximal end of the movable operating member 5 is pressed downward by a guide pin 6 in response to a reverse action of a bimetal 7. When a reset shaft 8 is pushed upward, the movable contact 3 is pressed upward, and the guide pin 6 is pressed upward so that the bimetal 7 can be returned to an initial state.