To intercept an electric path, even if a holding member that holds a displacement member for opening an electric path is disengaged.

A circuit breaker unit 90 is provided with two conductive electrodes 94a and 94b, in the lower part of a body 92 of a circuit breaker unit. The electrode 94b is provided with a conductive spring member 96, having thermal resistance and being extended toward the electrode 94a, and comprises an open portion 98, in which the spring member 96 is pushed against a pin 108 which contacts the electrode 94a with the electrode 94a to form an electric path. That is, the pin 108 transmits the force produced by a bimetal 110, which by reversing to the spring member 96, and thereby the open portion 98 is made to open, according to the displacement of the bimetal 110. In addition, the spring member 96 is made so sa to disengage itself from the electrode 94a by own elastic force, when it is in a state of not receiving external force.