To reduce the influence on the entire steering device due to the collision between a worm and a worm wheel caused by the inertia of a motor even if the steering of a steering wheel reaches its maximum and it gets in the state of an end butting.

The electric power steering device includes: a motor 8; a small-diameter gear 21, which is provided on the output shaft 24 of the motor 8; and a large-diameter gear 22, which engages with the small-diameter gear 21 and is attached to a steering shaft, wherein the power steering device assists the steering by a steering wheel by the rotation of the motor 8. In the device, the output shaft 24 of the motor 8 is provided with a rotation regulating mechanism 30, and regulates the rotation of the output shaft 24 rotated by the motor 8, with the amount of rotation corresponding to the maximum amount of steering of the steering wheel.