PURPOSE: To prevent the pushing of a closing button by mistake in the condition where a circuit breaker is closed by providing a stopper fixed on a connection lever interlocked with a switching lever between the closing button and a latch lever.

CONSTITUTION: A cam 13 energized by a closing spring 17 to rotate is set rotatable by a latch lever 18 rotated by pushing a closing button 24, so a switching lever 10 is rotated to switch a circuit breaker 1 through a rod 7, a conversion lever 3, and a movable rod 2. In such an operation mechanism for the circuit breaker 1, a connection lever 25 is provided to be interlocked with the switching lever 10, and a stopper 26 is fixed to a forward end part of it. In the condition where the circuit breaker 1 is closed, the switching lever 10 is rotated upward by the cam 13 to move the connection lever 25 up, so the stopper 26 is interposed between the closing button 24 and the latch lever 18. In the condition where the circuit breaker 1 is disconnected, the connection lever 25 is moved down, and the stopper 26 is moved downward from between the closing button 24 and the latch lever 18.