A retractable safety belt system for restraining a vehicle occupant in a seat comprising a seat belt secured at one end to a reel of an electric-motor driven retractor. The retractor motor is controlled by control means (9) having a drive circuit (92G) and a reverse rotation or protraction rotation detection circuit (94A) which senses the reverse rotation of the motor as the seat belt is protracted and energizes the motor to retract the seat belt, thereby removing any slack in the seat belt. Preferably, the control means includes an increasing voltage circuit (94C) for gradually increasing the voltage applied to the motor, thereby reducing the motor torque at the initial stage of retraction. Also, the control means preferably includes a load sensing circuit (94B) which de-energizes the motor as the load on the motor and, hence, the tension in the seat belt reaches a predetermined level.