Provided are a seat belt retractor and a seat belt apparatus the number of components of which can be reduced and the size and weight of which can be reduced. A pretensioner 5 includes a rotor 51 that is connected coaxially with a spool 2 and that has a plurality of engaging teeth 51a formed on the outer periphery thereof, a power generating means 52 that engages with the engaging teeth 51a and rotates the rotor 51, and a cover member 53 that houses at least the rotor 51, and the cover member 53 is disposed inside the base frame 3, and can bear the spool 2.