Disclosed is an electric power steering apparatus which includes: a steering shaft connected to a steering wheel of a vehicle; an electric motor for supplying auxiliary steering power; a direction sensor including a light emitting unit and a light receiving unit which face each other; a rotary member interposed between the light emitting unit and the light receiving unit, having at least one slot and rotating as the steering shaft rotates; a motor position sensor for detecting a rotation angle of a rotation shaft of the electric motor; and a control unit receiving electric signals from the direction sensor and the motor position sensor to calculate a steering angle.