A seat reclining device which includes: a guide bracket attached to one of a seat cushion and a seat back and having a plurality of guide wall portions (23a-23d) arranged in a circumferential direction at intervals; an internal gear attached to the other of the seat cushion and the seat back; and a mounting ring having a peripheral surface portion and a ring-shaped bottom surface portion, the peripheral surface portion being fixed to an outer peripheral surface of one of the guide bracket and the internal gear , and the ring-shaped bottom surface portion protruding inward from the peripheral surface portion and being disposed on an outer surface side of the other of the guide bracket and the internal gear , and which supports the seat back so as to allow the seat back to recline with respect to the seat cushion by relative rotation of the guide bracket and the internal gear , the seat reclining device comprising: a lock mechanism including lock plates (60A-60D) which are disposed in guide groove portions (23f-23i) between the adjacent guide wall portions (23a-23d) provided on the guide bracket , so as to be operable in a radial direction and which each have an outer peripheral surface provided with external teeth engageable with internal teeth of the internal gear ; characterized by an outer rolling member disposed between the ring-shaped bottom surface portion of the mounting ring and the outer surface of the guide bracket or the outer surface of the internal gear, that faces the ring-shaped bottom surface portion; and an inner rolling member disposed between opposed surfaces of the guide groove portion (23f-23i) of the guide bracket and the lock plate (60A-60D) and rollable in the radial direction together with the lock plate (60A-60D), wherein, while the outer rolling member and the inner rolling member press stacked members including the internal gear , the lock plates (60A-60D), and the mounting ring in a stacking direction relatively to one another to reduce wobbling, the outer rolling member causes rolling friction to act between the one of the guide bracket and the internal gear that rotates together with the mounting ring and the other that rotates relatively to the one of the guide bracket and the internal gear , and the inner rolling member causes rolling friction to act between the guide groove portion (23f-23i) and the lock plate (60A-60D). a lock mechanism including lock plates (60A-60D) which are disposed in guide groove portions (23f-23i) between the adjacent guide wall portions (23a-23d) provided on the guide bracket , so as to be operable in a radial direction and which each have an outer peripheral surface provided with external teeth engageable with internal teeth of the internal gear ; characterized by an outer rolling member disposed between the ring-shaped bottom surface portion of the mounting ring and the outer surface of the guide bracket or the outer surface of the internal gear, that faces the ring-shaped bottom surface portion; and an inner rolling member disposed between opposed surfaces of the guide groove portion (23f-23i) of the guide bracket and the lock plate (60A-60D) and rollable in the radial direction together with the lock plate (60A-60D), wherein, while the outer rolling member and the inner rolling member press stacked members including the internal gear , the lock plates (60A-60D), and the mounting ring in a stacking direction relatively to one another to reduce wobbling, the outer rolling member causes rolling friction to act between the one of the guide bracket and the internal gear that rotates together with the mounting ring and the other that rotates relatively to the one of the guide bracket and the internal gear , and the inner rolling member causes rolling friction to act between the guide groove portion (23f-23i) and the lock plate (60A-60D). <EOS>