A seat reclining apparatus for vehicles includes a casing, which has a recess and a mount extending from the recess, and a cap, which has a fringe and an inside gear formed along the inner periphery of the cap. The cap is received in the recess of the casing. The fringe of the cap and the periphery of the casing are held together by a binding frame so as not to separate from each other. The binding frame has a groove, and the fringe of the cap and the periphery of the casing are received in the groove. A lock mechanism is placed in the recess of the casing. The lock mechanism includes one or more lock gears. Each lock gear has arched gear teeth, and is movable between a meshed position, at which the lock gear is meshed with the inside gear of the cap, and a retracted position, at which the lock gear is disengaged from the inside gear. A driving shaft penetrating through the cap and the casing. By rotating the driving shaft in prescribed directions, the lock gear is meshed with or disengaged from the inside gear.