An occupant restraint system which is activated instantaneously at an vehicle accident to protect an occupant's body against a disaster. An occupant restraint system (A) is provided on the back (1a) of a seat (1) with a shoulder top restraint device (4) for restraining the right shoulder portion of the occupant (2). The occupant restraint system (A) is provided on the side portion of the back (1a) of the seat (1) with a shoulder side restraint device (5A), which includes: a motor (12) adapted to be actuated by a sense signal of a motor vehicle accident; an instantaneous turning mechanism unit (13) driven by the motor (12); bifurcated arms (14A) mounted on the instantaneous turning mechanism unit (13); and a shoulder receiving portion (15A) mounted on the other ends of the bifurcated arms (14A) for protecting the shoulder side (3b) of the body of the occupant (2).