A power steering device (100) is provided with: a worm shaft (2) rotated by the drive of an electric motor (7); a worm wheel (1) meshing with the worm shaft (2) and transmitting the rotational force of the electric motor (7) to a rack shaft for steering a wheel; a bearing for rotatably supporting the front end side of the worm shaft (2); a gear case (3) for housing the worm shaft (2); a pressing member for pressing the worm shaft (2) toward the worm wheel (1) with the bearing therebetween; and a holder (30) having a housing hole for housing the bearing so that the bearing is movable in the direction of pressing by means of the pressing member. The holder (30) has protrusions (33e) formed protruding toward the outside radially and in contact with the inner peripheral surface of the gear case (3).