A removable steering angle sensor for a motor-driven power steering apparatus for use in a vehicle intended for rough road use. The handlebar of the vehicle is disposed on an upper portion of a steering shaft, and a motor-driven power steering apparatus, including a power assist portion as an actuator unit, is disposed in a middle portion of the steering shaft. The steering angle sensor for detecting a steering angle is disposed on one end of the steering shaft, or more specifically, on a lower end portion of an output shaft, or a leading end portion of an output shaft. During maintenance, this arrangement provides for easy removal and installation of the steering angle sensor.