A rack shaft (110) has a rolling contact surface (110b) on the opposite side of rack teeth (110a) across an axis line X, and a pair of slanted surfaces (110c, 110c) extending in parallel with the axis line across the rolling contact surface (110b). Furthermore, a roller (123) rolling on the rolling contact surface (110b) of the rack shaft (110) and an urging member (130) having contact with the pair of slanted surfaces (110c, 110c) for applying an urging force are provided. The urging member (130) is attached to the housing (101), forms an annular configuration surrounding the entire circumference of the rack shaft (110), and has contact portions (130b, 130b) having contact with the pair of slanted surfaces (110c, 110c) to apply the urging force. Therefore, the force exerted on the rack shaft (110) by a pinion (103a) can be supported by a cylindrical roller (123) contacting with the rolling contact surface (110b). Moreover, it is possible to restrain a rotational displacement of the rack shaft (110) about the axis line by applying the urging force against the pair of slanted surfaces (110c, 110c) of the rack shaft (110) by the contacting portions (130b, 130b) of the urging member (130). Also, since the urging member (130) has an annular configuration, it is advantageously possible to easily attach or detach the urging member (130) to or from the housing (101) without using a connecting member such as adhesive or a screw.