Abstract: A circuit breaker includes a switching mechanism, a manual operating handle connected to the switching mechanism, and an instantaneous tripping device for detecting a short circuit current and opening contacts of a main circuit. The instantaneous tripping device and a latch receiver of the switching mechanism are connected with each other via a trip member capable of sliding up and down. Further, the circuit breaker includes a trip indicating member moving along with the trip member, and a trip indicating window formed in a breaker housing and facing the trip indicating member. The trip indicating member moves to an indicating position to visually indicate a tripping state of the circuit breaker through the trip indicating window when the circuit breaker member instantaneously trips.