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 64 connected to a detection circuit, allowing the electric power circuit to conduct when the detection terminal 64 becomes a connection state, while allowing the electric power circuit not to conduct when the detection terminal 64 becomes a non-connection state. The detection terminal 64 shifts from a connection state to a non-connection state in an interlocking relation with the rotation operation of the lever 30 in a detaching process of the lever side connector 20.