PURPOSE: To facilitate the extension of breakers in the same power source system, and enable the extension under the power source charging condition by installing plural case bodies so as to be connected to each other.

CONSTITUTION: Wiring circuit breakers 1 and 2 are provided. The breaker 1 is provided with a power source connecting terminal 3 for supplying the power from a power source, a female terminal 5 for main line for dividing a primary main line 4 to the breaker 2 for power supply, and a connecting terminal 6 for load for supplying the power to a load. The breaker 2 is provided with a male terminal 7 to be connected to the terminal 5, a female terminal 5 for dividing a primary main line 8 for power supply, and a connecting terminal 6 for load. The breakers 1, 2 are fitted to a projecting rail 10, which is fitted to a frame, by using a recessed fitting groove 11. At the time of extending breakers with the extension of load, the breaker 2b is used to slide on the rail 10, and the breakers 2a, 2b are connected to each other.