a seat reclining device has an external gear member and an internal gear member positioned in opposing relation , and a stopper member between the opposing gear members for regulating the reclining movement of the backrest relative to the seat cushion . the stopper member includes a first convex portion on the external gear member and a stopper provided on the outer peripheral surface of the internal gear member . a second convex portion is also provided on the external gear member . by engaging the second convex portion with a bore on a ring member that surrounds the periphery of the internal and external gear members , a part of the contact force between the stopper and the first convex portion is transmitted to the ring member .