a housing receiving a steering shaft and having a first step formed on an inner circumferential surface thereof as a diameter thereof is reduced toward one axial direction such that the first step has a first step surface perpendicular to the one axial direction and facing an opposite axial direction;

a first bearing including a first outer ring and a first inner ring, the first outer ring having a one-axial-direction side surface supported by the first step surface and the first inner ring coupled to an outer circumferential surface of the steering shaft; and

a first coupling member coupled to the outer circumferential surface of the steering shaft and supporting an opposite-axial-direction side surface of the first inner ring,

wherein the first step surface of the housing supports the one-axial-direction side surface of the first outer ring toward the opposite axial direction and the first coupling member supports the opposite-axial-direction side surface of the first inner ring toward the one axial direction.