Seat belt retractor

In order to provide a seat belt retractor which achieves a more stable performance of a pretensioner, a seat belt retractor has a spool (2) for winding up a belt (S) thereon. The spool (2) has a shaft portion (2A), a spool gear (2B), and a spring-biased shaft projection (2C) which are disposed to project from a face of the spool (2). A spool bearing (ring-like collar) (30) is fitted around the shaft portion (2A) of the spool (2). The spool bearing (30) is made of a material having high hardness and high rigidity such as SUS, SPCC (SPHC), or SC. By this spool bearing 30, the spool (2) is prevented from being directly subjected to load, like a bearing.