A webbing retractor which, by causing relative rotation between a prime mover rotating body and a rotating disc, connects the prime mover rotating body and a driven shaft which is connected to a take-up shaft of a webbing belt. A planet gear is pivotally supported at a plate having a braking piece and meshes with a sun gear. The plate is supported so as to be swingable around the sun gear. When the sun gear is driven to rotate at greater than a predetermined speed, the planet gear begins to circle around the sun gear against urging force of a spring attached to the plate, and makes the plate rotate such that the braking piece slidingly contacts the friction ring. Due to this braking, the rotating disc connected to the friction ring rotates relative to the prime mover rotating body.