To provide an actuator for a valve capable of cutting off power supply to an unexcited operation type electromagnetic brake after a specific time passes after a valve element of a valve stops in a closing or opening position.

In this actuator for the valve provided with the unexcited operation type electromagnetic brake, when opening and closing the valve by driving of a motor, a flat spiral spring is rolled in, and the valve is closed or opened by restoring force of the flat spiral spring in an emergency, and rewind of the flat spiral spring is checked when carrying no electric current, and only when carrying an electric current by an emergency signal from an extenal part, the rewind checking action of the flat spiral spring is released. The actuator is constituted so as to cut off the power supply to the unexcited operation type electromagnetic brake after the specific time passes after the valve element of the valve stops in the closing or opening position.