A seat reclining apparatus (4, 50) for a vehicle, comprising: a first plate adapted to be attached to one of a seat cushion and a seat back and including an internal gear; a second plate adapted to be attached to the other of the seat cushion and the seat back and including an external gear having fewer teeth than the internal gear and engaging with the internal gear; and characterized in that it also comprises a pair of wedge members (26; 27, 51; 52) arranged between the first plate and the second plate, biased in a direction in which eccentricity between the internal gear and the external gear increases, and retaining an engagement position between the internal gear and the external gear; and a driving cam arranged to be rotatable relatively to the first plate, including a cam portion, and to shift the engagement position between the internal gear and the external gear by the cam portion pressing the pair of wedge members (26; 27, 51; 52) so that the wedge members (26; 27, 51; 52) are integrally rotated with the cam portion when the driving cam is rotatably operated, wherein each of the wedge members (26; 27, 51; 52) includes a retaining portion (26a; 27a, 51a; 52a) and a pressed portion (26b; 27b, 51b; 52b) that are integrally formed with each other, the retaining portion (26a; 27a, 51a; 52a) being provided in a position axially overlapping the internal gear and the external gear and retaining the engagement position between the internal gear and the external gear, the pressed portion (26b; 27b, 51b; 52b) being axially offset from the retaining portion (26a; 27a, 51a; 52a) and pressed by the cam portion, and the seat reclining apparatus (4, 50) further comprising: a protruding column portion provided in the center of the first plate in a protruding manner and positioned coaxially with the internal gear; and a torsion spring including a coil portion disposed in a position axially overlapping the pressed portions (26b; 27b, 51b; 52b) and attached around an outer circumferential surface of the protruding column portion, the torsion spring including both ends, each of the ends being circumferentially adjacent to the cam portion and the pressed portion (26b; 27b, 51b; 52b) and disposed therebetween, the torsion spring being elastically deformed to reduce a frictional engagement between the coil portion and the protruding column portion when the cam portion presses the pressed portion (26b; 27b, 51b; 52b) via the end, the torsion spring being elastically deformed to increase the frictional engagement between the coil portion and the protruding column portion when the pressed portion (26b; 27b, 51b; 52b) presses the end. a first plate adapted to be attached to one of a seat cushion and a seat back and including an internal gear; a second plate adapted to be attached to the other of the seat cushion and the seat back and including an external gear having fewer teeth than the internal gear and engaging with the internal gear; and characterized in that it also comprises a pair of wedge members (26; 27, 51; 52) arranged between the first plate and the second plate, biased in a direction in which eccentricity between the internal gear and the external gear increases, and retaining an engagement position between the internal gear and the external gear; and a driving cam arranged to be rotatable relatively to the first plate, including a cam portion, and to shift the engagement position between the internal gear and the external gear by the cam portion pressing the pair of wedge members (26; 27, 51; 52) so that the wedge members (26; 27, 51; 52) are integrally rotated with the cam portion when the driving cam is rotatably operated, wherein each of the wedge members (26; 27, 51; 52) includes a retaining portion (26a; 27a, 51a; 52a) and a pressed portion (26b; 27b, 51b; 52b) that are integrally formed with each other, the retaining portion (26a; 27a, 51a; 52a) being provided in a position axially overlapping the internal gear and the external gear and retaining the engagement position between the internal gear and the external gear, the pressed portion (26b; 27b, 51b; 52b) being axially offset from the retaining portion (26a; 27a, 51a; 52a) and pressed by the cam portion, and a protruding column portion provided in the center of the first plate in a protruding manner and positioned coaxially with the internal gear; and a torsion spring including a coil portion disposed in a position axially overlapping the pressed portions (26b; 27b, 51b; 52b) and attached around an outer circumferential surface of the protruding column portion, the torsion spring including both ends, each of the ends being circumferentially adjacent to the cam portion and the pressed portion (26b; 27b, 51b; 52b) and disposed therebetween, the torsion spring being elastically deformed to reduce a frictional engagement between the coil portion and the protruding column portion when the cam portion presses the pressed portion (26b; 27b, 51b; 52b) via the end, the torsion spring being elastically deformed to increase the frictional engagement between the coil portion and the protruding column portion when the pressed portion (26b; 27b, 51b; 52b) presses the end.