To provide a breaker capable of reporting an erroneous operation if an opening/closing mechanism part is transitioned to an open state when a protective shutdown detection circuit fails to report an alarm signal, and not reporting an erroneous operation when the opening/closing mechanism part is manually opened.

The breaker 100 is provided with a breaker body 1 that includes: an opening/closing mechanism part 4 for opening/closing a main circuit between a power supply side and a load side; a switch (open/closed status output part) 5 for outputting the open/closed state of the opening/closing mechanism part 4 in conjunction with the operation of the opening/closing mechanism part 4; a protective shutdown detection circuit 2 for detecting a flow of a current exceeding a prescribed value through the main circuit to open the opening/closing mechanism part 4 and to report an alarm signal to the outside (a control station); and an erroneous operation report part 3 for reporting an erroneous operation to the outside if the opening/closing mechanism part 4 is transitioned to a open state when the protective shutdown detection circuit 2 fails to report an alarm signal.