To provide a circuit breaker capable of surely breaking a circuit not only in the case of contact point fusion adherence but also in the cases of troubles such as a delay in the action of a movable contact piece and the breakage of the movable contact piece.

The circuit breaker includes a fixed contact point 10, and the movable contact point 20 which is brought into contact with or separated from the fixed contact point 10 owing to a thermal effect. A fusible metal portion 121 that is fused by a flow of current of a given value or higher is interposed in the base end 12 of the fixed contact point 10. Part of the base end 12 including the fusible metal portion 121 is buried and fixed in a resin block 6.