To enable a stored electric circuit to be put into a cutoff state when the door of a switchboard is opened, without restriction on the installing position of apparatus and device, without increasing the dimensions of the switchboard or causing extra assembling time.

A door switch 15, which is turned off only when a door is completely closed, is connected to the shunt trip coil 12 of a concealed breaker 11. If the door is opened during operation, the door switch 15 is turned on to trip the the breaker 11. If a canceling switch is connected in series to this door switch 15, it becomes possible to cancel the action of the door switch 15 in accordance with the opening or shutting of the door. Also, a door switch 25, which is turned on only when the door is completely closed, is connected to the undervoltage trip coil 22 of the breaker 21. If the door is opened during operation, the door switch 25 is turned off to trip the breaker 21. If the canceling switch is connected in parallel to this door switch 25, it becomes possible to cancel the action of the door switch 25.