A seat reclining apparatus (10, 30, 50) for a vehicle for connecting a seat back and a seat cushion configuring a seat for the vehicle in a relatively rotatable manner, the seat reclining apparatus comprising: an inner gear plate being provided with inner teeth and a center cylindrical portion, the inner gear plate configured to be joined with the seat back; an outer gear plate being provided with a smaller number of outer teeth than a number of the inner teeth and including a center opening, the outer gear plate being rotatably mounted to the inner gear plate while shifting a meshing position relative to the inner gear plate in a state where the center cylindrical portion of the inner gear plate is positioned within the center opening and the outer teeth and the inner teeth are meshed with one another, the outer gear plate configured to be joined with the seat cushion; a first wedge member and a second wedge member being positioned within a clearance formed between a peripheral of the center opening of the outer gear plate and the center cylindrical portion of the inner gear plate while the outer teeth and the inner teeth are meshed with one another; characterised by a third wedge member (17, 59a) and a fourth wedge member (18, 59b) being positioned within respective spaces (15a, 16a) formed between the first wedge member and the center cylindrical portion of the inner gear plate, and the second wedge member and the center cylindrical portion of the inner gear plate, respectively; a first biasing member biasing the third wedge member (17, 59a) and the fourth wedge member (18, 59b) in a direction wherein the respective spaces (15a, 16a) are narrower while biasing the first wedge member and the second wedge member in the direction wherein the clearance is narrower, the first biasing member locking a relative rotation of the inner gear plate and the outer gear plate; and an operating portion (5, 6, 20) allowing the relative rotation of the outer gear plate and the inner gear plate by shifting one of the third wedge member (17, 59a) and the fourth wedge member (18, 59b) against biasing force applied by the first biasing member and by rotationally shifting one of the first wedge member and the second wedge member corresponding to a selected one of the third wedge member (17, 59a) and the fourth wedge member (18, 59b) against biasing force applied by the first biasing member. an inner gear plate being provided with inner teeth and a center cylindrical portion, the inner gear plate configured to be joined with the seat back; an outer gear plate being provided with a smaller number of outer teeth than a number of the inner teeth and including a center opening, the outer gear plate being rotatably mounted to the inner gear plate while shifting a meshing position relative to the inner gear plate in a state where the center cylindrical portion of the inner gear plate is positioned within the center opening and the outer teeth and the inner teeth are meshed with one another, the outer gear plate configured to be joined with the seat cushion; a first wedge member and a second wedge member being positioned within a clearance formed between a peripheral of the center opening of the outer gear plate and the center cylindrical portion of the inner gear plate while the outer teeth and the inner teeth are meshed with one another; characterised by a third wedge member (17, 59a) and a fourth wedge member (18, 59b) being positioned within respective spaces (15a, 16a) formed between the first wedge member and the center cylindrical portion of the inner gear plate, and the second wedge member and the center cylindrical portion of the inner gear plate, respectively; a first biasing member biasing the third wedge member (17, 59a) and the fourth wedge member (18, 59b) in a direction wherein the respective spaces (15a, 16a) are narrower while biasing the first wedge member and the second wedge member in the direction wherein the clearance is narrower, the first biasing member locking a relative rotation of the inner gear plate and the outer gear plate; and an operating portion (5, 6, 20) allowing the relative rotation of the outer gear plate and the inner gear plate by shifting one of the third wedge member (17, 59a) and the fourth wedge member (18, 59b) against biasing force applied by the first biasing member and by rotationally shifting one of the first wedge member and the second wedge member corresponding to a selected one of the third wedge member (17, 59a) and the fourth wedge member (18, 59b) against biasing force applied by the first biasing member.