To prevent the loss of a terminal cover, and facilitate the opening/ closing of the terminal cover to a circuit breaker, by integrally forming a terminal cover, covering the connecting part between the circuit breaker and an extended terminal, with a base for maintaining the circuit breaker and the extended terminal.

In this circuit breaker a terminal cover 1a is integrally formed with an insulated base 2 holding an extended terminal 13, and the base 2 holding the terminal 13 and a terminal cover 1 are connected by an elastically deformable narrow part. By thus forming the cover 1 integrally with the base 2, the loss of the cover 1 can be prevented, and also workability at the time of maintenance and inspection in a narrow board can be improved, because the cover 1 is released from the direction wherein a terminal screw 21 is tightened.