To provide a small motor-operated valve which can control a high flow, there is provided a motor-operated valve of which a body has an orifice, seat and a valve element provided opposite to the seat. The valve element is operated by a driver which is driven to rotate by an output gear to which the rotation of a rotor having been reduced by means of a mechanical paradox planetary gear mechanism is transmitted. To force the valve element in the direction in which the valve is opened, a coil spring is disposed in a bore formed in the upper portion of the body oppositely to a bush.