In a power steering apparatus, a basic-target-rotational-speed setting portion 42 sets a basic target rotational speed Rb of an electric motor 27 on the basis of the vehicle speed and the angular velocity of steering. A temperature-coefficient setting portion 43 sets a temperature coefficient which becomes smaller with an increase in the temperature. A target-rotational-speed setting portion 44 sets a target rotational speed R of the electric motor 27 on the basis of the formula R=Rb. A motor-drive control portion 45 controls a drive circuit 28 so that this target rotational speed R will be attained.