A seat belt retractor that functions to cancel both a function of a vehicle sensor and a function of a webbing sensor on a predetermined condition with a simple structure and a small number of components. When a seat belt is fully retracted, a cam follower of a first lever comes into contact with a second cam portion of a cam plate. An actuator pressing portion of the first lever presses an actuator of a vehicle sensor to a non-operation position. The function of the vehicle sensor is thereby cancelled. Further, when an engaging claw of a second lever separates from a ratchet tooth of a ring gear, the ring gear is allowed to rotate in a seat belt withdrawing direction. Therefore, the function of the webbing sensor is cancelled.