To provide a thermally-actuated switching device which completely blocks a current and holds such a state that a movable contact is separated from a fixed contact even if the temperature of an operating part composed of a bimetal has decreased when the movable contact is separated from the fixed contact by deformation caused by the generated heat of the operating part itself.

The switching device comprises the operating part 7 formed to the bimetal member 6, the movable contact 10 provided on the operating part 7, the fixed contact 11 which the movable contact 10 is contacted with and separated from, and a return-obstructing part 8 which is formed to the bimetal member 6, deforms by its own temperature increase and returns by its temperature decrease, and which retreats from the operating part 7 at the deformation time and allows the deformation and obstructs the return of the operating part 7 at the non-deformation time. The temperature where the operating part 7 returns is set at a higher temperature than that at which the return-obstructing part 8 returns.