The present invention is directed toward a circuit breaker having an open-and-close shaft; holding member coupled to the open-and-close shaft; at least one movable contactor coupled to the holding member; support member for rotatably supporting the open-and-close shaft; and stopper member coupled with the support member so as to restrict an open-and-separation position of the movable contactor, wherein the circuit breaker is disposed within a case, the stopper member are formed on side faces of between-phase partitions of the case and a portion of the holding member contacts the stopper member. Thereby, it is possible to improve an insulation function and to lessen the impact between the holding member and the stopper member.