A vehicle seat reclining apparatus comprises a base member to be connected to one of a seat cushion and a seat back, a rotation member which is to be connected to the other of the seat cushion and seat back, which is arranged to rotate relative to the base member and which includes an internal gear, a regulating member to regulate axial movement of the rotation member relative to the base member, and a locking setup which includes an external gear and which is arranged to move between a lock position to engage the external gear with the internal gear and an unlock position for disengagement. The base member includes an outer circumferential portion defining a circular recess, the rotation member includes an outer circumferential portion including a cylindrical portion fit rotatably in the outer circumferential portion of the base member. The outer circumferential portion of the rotation member further includes a flange portion which projects radially outwards from the cylindrical portion, which is placed axially between the regulating member and the outer circumferential portion of the base member and which includes a side surface facing away from the base member and servings as a sliding regulation surface set in sliding contact with the regulating member.