To provide an electric power circuit breaker device capable of breaking an electric circuit by only one action such as a rotation operation of a lever.
A service plug 10 for breaking an electric power circuit by detaching a lever side connector 20 from a stand-by side connector 50 comprises: a lever 30 turnably supported to the lever side connector 20; and a coupling detector 40 provided on the lever 30, having a short terminal 44 connected to a detection circuit, allowing the electric power circuit to conduct by closing the detection circuit, while allowing the electric power circuit not to conduct by opening a detection terminal 64. The short terminal 44 shifts from a connection state in which the short terminal 44 is connected to the detection circuit to a non-connection state in which the short terminal 44 is not connected to the detection circuit by only rotating the lever 30 in a detaching process of the lever side connector 20, and then the electric power circuit is not conductive by the same operation of the lever.