Abstract: A lock mechanism for a webbing retractor is designed to prevent unwinding of an occupant restraining webbing for a vehicle when an emergency situation of the vehicle occurs. The lock mechanism has a lock wheel adapted to rotate by means of biasing force in unison with the rotation of a webbing take-up shaft in a direction in which the webbing is unwound, and a pawl lever activated by the action of an acceleration sensor to engage with the lock wheel, thereby causing the rotation of the lock wheel to be delayed with respect to the rotation of the take-up shaft, and thus stopping the take-up shaft from rotating in the webbing unwinding direction. The lock mechanism further has a leaf spring member adapted to receive the rotational force from the take-up shaft through friction at three points and limit the action of the pawl lever when the take-up shaft rotates in a direction in which the webbing is wound up.