Abstract: A reclining angle adjustment device for a seat includes a shaft having a concentric portion and an eccentric portion and rotatable for adjusting the reclining angle of the seat, a tapered bushing having a tapered inner peripheral surface engaging the eccentric portion along the shaft, a gear train including an external gear and an internal gear meshing with the internal gear, the internal gear having more teeth than the external gear, a first arm having one of the external and internal gears which is rotatably fitted at its center over the concentric portion, and a second arm having the other gear which is rotatably fitted at its center over the tapered bushing. A resilient member normally presses the tapered bushing axially of the shaft in a direction to strengthen meshing engagement between the external and internal gears.