The disclosed seat belt retractor and device can be useful to reliably warn the vehicle occupant of various hazards, such as obstacles or the dozing of the driver. The seat belt retractor and device can comprise an electric motor, a spool for retracting a seat belt to restrain a vehicle occupant, and a controller for controlling the driving of the electric motor. The controller can be configured to control the driving of the electric motor so that several operations for increasing and decreasing the tension acting on the seat belt by the spool are repeated for warning the vehicle occupant. In addition, the controller can be configured to control the driving of the electric motor so that a motion of the spool in a seat belt retracting direction is larger in an initial operation relative to subsequent operations.