Abstract: A seat belt retractor in which when a lock gear (13) rotates in a direction (B) relative to a reel shaft (4), a projecting shaft (19d) moves by the action of a first cam hole (13i), causing a main pawl (19) to pivot in the direction B. Thus, teeth (20a) which are to be engaged with first and second pawl portions (19b) and (19c) are decided. At this time, a backup pawl (22) does not pivot because a projecting shaft (21c) merely moves along a hole (13m). When the lock gear (13) further moves in the direction (B) relative to the reel shaft (4), the first and second pawl portions (19b) and (19c) begin to engage with the teeth (20a), and the projecting shaft (21c) moves along a radial hole (13k). Thus, the backup pawl (22) pivots in the direction (B), and a tooth (2f) which is to be engaged with the backup pawl (22) is decided.