A thermally responsive switch includes a hermetic container including a housing and a header plate hermetically secured to an open end of the housing, a conductive terminal pin inserted through the header plate, a conductive pin, a thermally responsive plate having one of two ends fixed to the terminal pin, a movable contact secured to the other end of the thermally responsive plate, and a fixed contact fixed via an electrical conductor to the terminal pin, the conductor having a fuse part and a heater. The fixed contact is fixed to a ceramic member disposed between the container and the fixed contact. The housing includes a bottom surface including both lengthwise ends between which the conductive pin is interposed. Both ends of the housing bottom surface are deformed axially relative to the conductive pin from an initial state, so that an operating temperature of the switch is calibratable.