CIRCUIT BREAKER

A circuit breaker (1) is provided with a mechanism unit (6) for opening/closing an electrical circuit, a command output unit (40) for outputting an operation command to operate the mechanism unit (6), a switch unit (15) operating upon completion of the operation of the mechanism unit based on the operation command, and an abnormality detection unit (16). The abnormality detection unit (16) detects an abnormality of the mechanism unit (6) on the basis of the difference between timing at which the operation command is output from the command output unit (40) and timing at which the switch unit (15) operates. 断路器(1)具有：机构部(6)，其进行电路的开闭；指令输出部(40)，其输出使机构部(6)动作的动作指令；开关部(15)，其与基于动作指令的机构部的动作的完成联动而动作；以及异常检测部(16)。异常检测部(16)基于从指令输出部(40)输出动作指令的定时和开关部(15)进行动作的定时的差，对机构部(6)的异常进行检测。