A breaker (1) is provided with: a fixed piece (2) which has a fixed contact; a movable piece which has a movable contact at a front end portion and pushes the movable contact against the fixed contact to bring same into contact with each other; a thermally responsive element that deforms in accordance with a change in temperature and thereby actuates the movable piece so that the movable contact separates from the fixed contact; and a case body (71) of a resin case that accommodates the fixed piece (2), the movable piece, and the thermally responsive element. The case body (71) has recess portions (75, 77) which are recessed from a peripheral portion, and the fixed piece (2) has a withdrawal portion (25) that withdraws from the recess portions (75, 77) of the case body (71) by a predetermined first distance (D1) or more, and is embedded in the case body (71).