A power steering device includes: first and second load transition regions provided in first and second predetermined ranges in a nut side ball screw groove from the other end side openings of the first and second connection passages along the nut ball screw groove, formed so that radial distances between a rotation axis of the nut and the nut side ball screw groove are gradually increased toward the other end side opening of the first and second connection passages, and formed so that the balls pass through first and second no load regions, and then pass through a first load region, when the balls in the first and second predetermined ranges are moved from the other end side opening of the first and second connection passages along the nut side ball screw groove.