Abstract: An electrically driven power steering apparatus utilizes an electric motor as a drive source and produces an assisting torque which depends on the magnitude of a torque applied from steering mechanisms for assisting in the operation of a steering system. When an abnormality in the torque applied or a locking of the motor is detected, the energization of the motor is interrupted as is a system which transmits the assisting torque. In this manner, the application of a relative force to the steering system from the electric drive mechanism is blocked, thus positively preventing the vehicle from being steered against the intent of a driver as a result of influencs of any abnormal operation of the electric drive mechanism upon the steering system. Whenever the energization of the motor and the assisting torque transmission system are interrupted, the force required for the steering operation will be equivalent to a manual steering.