To provide a thermally-actuated switch with an airtight container having no influence from a fluctuated electric current passing through it.

This thermally-actuated switch 1 has an airtight container composed of a container 2 and a lid plate 3. A lead terminal pin 5 provided with a fixed contact part 6 is airtightly insulated and fixed to the lid part 3. A movable plate supporting body 7 to be rigidly combined with one end of a movable plate 8 is conductively secured to the lid plate 3. A movable contact 9 is inserted in a through hole provided on the free end of the movable plate 8 and in a through hole bored in the drawing center of a thermally- actuated plate 10. The movable contact 9 is fixed to the movable plate 8, and holds the thermally-actuated plate 10 by loose fitting between the head part 9A of the movable contact and the movable plate 8, in order to interlock the movable plate with an action of the thermally-actuated plate. Since an electric current does not practically pass through the thermally-actuated plate, even if it is attached to an appliance having a fluctuated electric current, a circuit can be cut off at a designated temperature.