Electric power steering system

If a pair of spur gears or helical even when it is constituted by the gear to achieve a predetermined reduction ratio, to provide an electric power steering apparatus capable of ensuring a sufficient gear strength with a simple structure. The rotational torque of the electric motor 7, and transmitted to the steering shaft in the driven gear 5 which is provided with the drive gear 6 and the steering shaft provided on the output shaft of the electric motor 7, in the electric power steering apparatus reduction ratio is 3 or more, the steering is axially disposed substantially in parallel to the output shaft and the electric motor 7, the axial distance between the two axes is at 90mm less than 35 mm, the drive gear 6, the number of teeth 6 to 15, the module is 0.8 or more 1 .5 or less, 2.4 times the tooth depth modules, the pressure angle is 14.5 degrees 30 degrees, the twist angle is less than 40 degrees 0 degrees.