A vehicle seat reclining structure comprising: a pair of lower arms provided on both left and right sides at a rear end of a seat portion of a vehicle seat; a pair of side frames rotatably supported respectively by the pair of lower arms and disposed on both left and right sides at a lower end of a seatback portion of the vehicle seat; a recliner provided around one of pivot support portions of the lower arms and the side frames for retaining the seatback portion at a desired angle forward or backward around the pivot support portion; and a stopper provided around the other one of pivot support portions of the lower arms and the side frames for restricting degree of inclination of the seatback portion forward or backward around the pivot support portion, wherein the stopper includes a plurality of arm-side abutment portions formed on the lower arm and a plurality of frame-side abutment portions formed on the side frame at such positions as to overlap each other on a rotating track around the pivot support portion; and the stopper is configured such that when the seatback portion is inclined at a predetermined angle, the plurality of arm-side abutment portions and the plurality of frame-side abutment portions abut on each other, wherein the plurality of arm-side abutment portions is formed on arm-side protrusions protruding from the lower arm toward the side frame, and is formed on at least one end face of the arm-side protrusions in a rotating direction around the pivot support portion, and wherein the plurality of frame-side abutment portions is formed on frame-side protrusions protruding from the side frame toward the lower arm, and is formed on at least one end face of the frame-side protrusions in a rotating direction around the pivot support portion, characterised in that the arm-side protrusions are formed by cutting and raising part of the lower arm, and both ends in a direction orthogonal to the rotating direction of the arm-side protrusions are coupled to a main body of the lower arm, and in that the frame-side protrusions are formed by cutting and raising part of the side frame, and both ends of the frame-side protrusions in a direction orthogonal to the rotating direction of the frame-side protrusions are coupled to a main body of the side frame. a pair of lower arms provided on both left and right sides at a rear end of a seat portion of a vehicle seat; a pair of side frames rotatably supported respectively by the pair of lower arms and disposed on both left and right sides at a lower end of a seatback portion of the vehicle seat; a recliner provided around one of pivot support portions of the lower arms and the side frames for retaining the seatback portion at a desired angle forward or backward around the pivot support portion; and a stopper provided around the other one of pivot support portions of the lower arms and the side frames for restricting degree of inclination of the seatback portion forward or backward around the pivot support portion, wherein the stopper includes a plurality of arm-side abutment portions formed on the lower arm and a plurality of frame-side abutment portions formed on the side frame at such positions as to overlap each other on a rotating track around the pivot support portion; and the stopper is configured such that when the seatback portion is inclined at a predetermined angle, the plurality of arm-side abutment portions and the plurality of frame-side abutment portions abut on each other, wherein the plurality of arm-side abutment portions is formed on arm-side protrusions protruding from the lower arm toward the side frame, and is formed on at least one end face of the arm-side protrusions in a rotating direction around the pivot support portion, and wherein the plurality of frame-side abutment portions is formed on frame-side protrusions protruding from the side frame toward the lower arm, and is formed on at least one end face of the frame-side protrusions in a rotating direction around the pivot support portion, characterised in that the arm-side protrusions are formed by cutting and raising part of the lower arm, and both ends in a direction orthogonal to the rotating direction of the arm-side protrusions are coupled to a main body of the lower arm, and in that the frame-side protrusions are formed by cutting and raising part of the side frame, and both ends of the frame-side protrusions in a direction orthogonal to the rotating direction of the frame-side protrusions are coupled to a main body of the side frame.