A power steering apparatus has a first actuator provided as a multi-phase rotating electric machine and disposed on a steering column side of an intermediate shaft and a second actuator disposed on a rack gear side thereof. A first ECU controls a drive of the first actuator and detects an abnormality of the first actuator. The first ECU changes an output of the first actuator based on a notification from a communication bus. The first ECU performs an initial diagnosis of the first actuator at a vehicle startup time for detecting abnormality, by supplying an electric power to the first actuator for not providing a torque to a steering wheel.