In a seat belt retractor according to the present invention, a first protruding shaft of a reel shaft is loosely fitted into a recess, which is formed in an end of an output shaft, in such a manner that there is a prescribed gap between the shaft and the inner wall of the recess. The output shaft and the reel shaft are loosely fitted together so as to be capable of moving relative to each other in the axial direction but incapable of rotating relative to each other in the rotational direction. Accordingly, the reel shaft is capable of pivoting about the end of the first protruding shaft, which is the loosely fitted end. When the reel shaft pivots in this manner, the teeth of a ratchet on one side engage with teeth formed on a wall on the same side.