Circuit breaker

A circuit breaker comprises a make-break contact for making and breaking an electrical circuit, an open-contact spring, a toggle mechanism, and an electromagnetic operation mechanism. The open-contact spring biases the make-break contact in the opening direction. When the make-break contact shifts from the open state to the closed state, a biasing force that biases the make-break contact in the opening direction increases. The toggle mechanism shifts the make-break contact from the open state to the closed state. The electromagnetic operation mechanism includes: a moving core (63) moving against the biasing force to thereby cause the toggle mechanism to shift the make-break contact from the open state to the closed state; and a fixed core (61) that has a first attraction surface (61a) for attracting the moving core (63) with an inter-surface distance (A) between the first attraction surface (61a) and the moving core (63) that is shorter than a moving distance (B) of the moving core (63).