A steering apparatus (S1, S100) comprising: a steered shaft supported by a housing so as to be slidable in an axial direction and configured to make a reciprocating motion in the axial direction to steer steered wheels; a ball screw mechanism including a rolling screw portion having a first screw groove (21b1) provided on an outer peripheral surface of the steered shaft, a rolling nut having a second screw groove (33a1) corresponding to the first screw groove (21b1) and provided on an inner peripheral surface of the rolling nut, and a plurality of rolling elements accommodated between the first screw groove (21b1) and the second screw groove (33a1); a motor fixed to the housing and provided with an output shaft that is offset from the steered shaft; a belt transmission mechanism including a drive pulley fixed to the output shaft so as to be rotatable together with the output shaft in an integrated manner and having first external teeth (35a1) provided on an outer periphery of the drive pulley, a driven pulley provided outside the rolling nut and having second external teeth (35c1) provided on an outer periphery of the driven pulley, and a toothed belt having internal teeth (35b1) meshed with the first external teeth (35a1) and the second external teeth (35c1) and configured to transmit a driving force between the drive pulley and the driven pulley; and a fixing mechanism (40, 140) configured to restrict relative rotation between the rolling nut and the driven pulley, wherein the fixing mechanism (40, 140) includes an internal thread (41, 141) provided on an inner peripheral surface of the driven pulley, characterized in that the fixing mechanism (40, 140) further includes: a cutout section (43, 143) provided in the driven pulley, at a position closer to a first end side of the driven pulley than the internal thread (41, 141), and configured to be open at least at a radially inner side of the driven pulley and an axially end side of the driven pulley in the axial direction, and a locknut (42, 142) including a locknut body (42, 142a) having an external thread (42d, 142d) screwed into the internal thread (41, 141), and a locking lug (42b, 142b) disposed in the cutout section (43, 143) and engaged with the driven pulley in a circumferential direction, wherein the cutout section (43, 143) is provided at a position offset in the axial direction from a range of the second external teeth (35c1) in the axial direction, and wherein the locknut (42, 142) includes the locknut body (42a, 142a), the locking lug (42b, 142b) that is a portion of a thin-wall cylindrical portion extending from the locknut body (42a, 142a) in the axial direction and thinner than the locknut body (42a, 142a), the locking lug (42b, 142b) being formed to extend outward in a radial direction, and engaged with the cutout section (43, 143) in the circumferential direction, and a remaining portion (42c, 142c) that is a portion of the thin-wall cylindrical portion other than the locking lug (42b, 142b). a cutout section (43, 143) provided in the driven pulley, at a position closer to a first end side of the driven pulley than the internal thread (41, 141), and configured to be open at least at a radially inner side of the driven pulley and an axially end side of the driven pulley in the axial direction, and a locknut (42, 142) including a locknut body (42, 142a) having an external thread (42d, 142d) screwed into the internal thread (41, 141), and a locking lug (42b, 142b) disposed in the cutout section (43, 143) and engaged with the driven pulley in a circumferential direction, wherein the cutout section (43, 143) is provided at a position offset in the axial direction from a range of the second external teeth (35c1) in the axial direction, and wherein the locknut (42, 142) includes the locknut body (42a, 142a), the locking lug (42b, 142b) that is a portion of a thin-wall cylindrical portion extending from the locknut body (42a, 142a) in the axial direction and thinner than the locknut body (42a, 142a), the locking lug (42b, 142b) being formed to extend outward in a radial direction, and engaged with the cutout section (43, 143) in the circumferential direction, and a remaining portion (42c, 142c) that is a portion of the thin-wall cylindrical portion other than the locking lug (42b, 142b).