A power steering device includes a first bearing and a second bearing that rotatably support the base-end side and the tip-end side of a worm shaft, a biasing member that biases the outer circumferential surface of the second bearing, and an elastic member that is arranged between the inner circumferential surface of a gear case and the outer circumferential surface of the second bearing. The inner circumferential surface of the gear case is formed such that the second bearing can move towards a worm wheel by the biasing force of the biasing member, the inner circumferential surface of the gear case is provided with a ring-like groove that houses the elastic member, and the center of the ring-like groove is offset towards the worm wheel side from the center axis of the worm shaft when the first bearing and the second bearing are in a coaxial state.