To provide a rotating member and a forming method thereof that allow formation of protrusions biting into an opposite surface to achieve high slip torque with a simple configuration. The rotating member includes a boss part and an anti-slip surface at least on one of both axial end faces of the boss part. The anti-slip surface has a plurality of corrugated rib parts, which includes a main groove and at least one auxiliary groove extending parallel to the main groove, with a ridge protruding higher than the anti-slip surface between the main groove and the auxiliary groove.