Method and apparatus for controlling a synchronous motor

A method and an apparatus for controlling a synchronous motor (1), by reading an advance angle X of the rotor (102) upon excitation of the synchronous motor (S11), reading an actual rotating speed N of the rotor (S12), reducing the advance angle (S14) when the detected actual rotating speed is higher than a target value Nmoku (S13), and increasing the advance angle (S16) when the detected actual rotating speed is lower than the target value (S15), so that the rotating speed N is controlled to the target value Nmoku. The apparatus is available at a reduced cost with a reduced number of components, and its control circuit is small-sized.