A recliner has a ratchet and a guide assembled together so as to be rotatable relative to each other, and a pawl supported by the guide in a circumferential direction. The pawl is adapted to inhibit rotational movement of the ratchet relative to the guide when moved to be pushed radially outwards. The pawl is supported by guide walls formed in the guide, and the guide walls are located at circumferentially opposite sides of the pawl. Each guide wall has a recessed part (weak portion) formed at a location spaced in the circumferential direction apart from a contact face of the guide wall which is in contact with the pawl. The recessed part is adapted to undergo local stress concentration and plastic deformation due to pressing force received from the pawl when a large load that causes the pawl to undergo forced deformation in the circumferential direction is applied.