To provide a circuit breaker capable of confirming the date of inspection.

A branch breaker 1 includes: a casing 1a housing a switch part 12 by inserting it between a primary side terminal part 10 and a secondary side terminal part 11; an operating section 13 for manual operation; a switch mechanism section 14 for opening/closing the switch part 12 in response to operation of the operating section 13; a release section 15 for releasing the switch part 12 when an unusual condition occurs; a current detecting part 17 for detecting the current flowing between the primary side terminal part 10 and the secondary side terminal part 11; a connecting terminal part 19, to which an inspecting device 6 is to be connected; and a computing section 18 which has a current computing section 180 for computing a current value of the electrical passage based on an output of detection by the current detecting part 17, a communicating section 181 for communicating with the inspecting device 6, and a memory section 183 and which transmits the measurement data showing the current value in response to a request from the inspecting device 6. The computing section 18 stores the data of the date of inspection, which is transmitted from the inspecting device 6 received the measurement data, in the memory section 183.