Abstract: To simplify the structure of a webbing retractor, at a second locking mechanism 44 of the webbing retractor, when a gas generator is not operated, a cam engages with an outer peripheral groove of a lock ring, and a limit load by a torsion shaft is made to be a high load. On the other hand, when the gas generator is operated, the cam is moved apart from the outer peripheral groove of the lock ring, and the limit load by the torsion shaft is made to be a low load. Because only the cam is interposed between the lock ring and a piston which is driven by the gas generator, the number of parts of the second locking mechanism can be reduced, and the structure of the second locking mechanism can be made simple.