an electric motor for generating a steering force in response to a command value, and a controller for generating said command value to said electric motor, wherein said controller generates said command value in correspondence with steering state of wheels, and thereby controls torque or rotation number of said electric motor, and

means for detecting said steering state of said wheels, and wherein, based on a detection result by said means for detecting said steering state, if the steering velocity of said wheels is larger than a predetermined value, said controller controls said command value so that a difference between a torque command value, which is said command value to said electric motor, and an actual torque of said electric motor will become smaller, and, if said steering velocity of said wheels is smaller than said predetermined value, said controller controls said command value so that a difference between a rotational velocity command value, which is said command value to said electric motor, and an actual rotational velocity of said electric motor will become smaller, and

wherein said controller inputs said steering state detected by said steering-state detection means, differentiates said steering state thereby to determine a differentiated value of the detected steering state, makes a comparison between said differentiated value and a threshold value thereby to make a judgment as to whether said steering state is in a holding operation state or a steering operation state, and creates a steering command signal of said holding operation if said steering state is in said holding operation state, and creates a steering command signal of said steering operation if said steering state is in said steering operation state, a holding-operation control or a steering-operation control being executed over said electric motor based on said steering command signal.