In an interrupter mechanism for automatic switch is an alarm output plate, which is arranged so that it can vertically along a frame (cover) of the circuit breaker mechanism to slide, fixed to the engaging projection of the cover plate via a pair of right and left guide holes which are formed therein. At the same time, one end of which is used in the Standby mode to a handle spring, to rotate an operating handle in a Abschaltanzeigestellung, trapped at the alarm output disk. When a Rastenaufnehmer is driven by an overcurrent detection section of the breaker mechanism or rotated, and the fixed state of the latch is eliminated by the electric circuit of the circuit breaker is interrupted due to the stored energy of a main spring, wherein the alarm output plate is driven in a lateral direction in this case, and thus, the fixed state of the alarm output plate so that the alarm output plate driven by the spring force of the handle spring upward, and an alarm contact is activated is eliminated.