To provide a thermally responsive latching device for latching a movable part without using any complex mechanism in which operation can be promptly activated, restrictions on using environment is less, an operating temperature can be strictly determined, and repeated usage is possible.

In the thermally responsive latching device for latching the movable part at a specified position in accordance with a prescribed temperature, the movable part is constituted of a flexible member at least part of which is coated by a heat activated member reversibly and repeatedly changeable between states of a solid phase and a liquid phase in accordance with temperature change. A constituent body has rigidity when the heat activated member is in the solid phase, and has flexibility when the heat activated member is in the liquid phase.