A parallel shaft gear mechanism (19a) for a steering assist of the present electric power steering apparatus (1) includes an idle gear (26) rotatably supported via a rolling bearing (39), on an outer peripheral surface (37d) of an intermediate shaft (37) supported by a rack housing (15). The idle gear (26) is arranged in an annular synthetic resin member (43) fixed on the outer peripheral surface (44a) of an outer ring (44) of the bearing (39). On the outer peripheral surface (44a) of the outer ring (44), a regulating portion (53, 53A, 53B, 53C, 53D, 53E, 53F, 53G, 54, 54A, 54B, 54C, 54D, 54E, 54F, 55, 56, 56A, 56B, 59, 59A, and 59B) for regulating relative rotation between the outer ring (44) and the synthetic resin member (43) is arranged. The synthetic resin member (43) is formed in a manner to cover the regulating portion on the outer peripheral surface (44a) of the outer ring (44), as a result of a molding process using a mold.