strip 5 in the inner space 1a back to the reel 27 therefore the seat belt 1 loses rigidity to make it free so that the seat belt 1 is retracted into the retractor 4 to go back to the initial full wound state or occupant restraining state then the wire 29 goes back to the initial state without loosening therebetween as the reel 27 rewinds the wire 29 referring to fig1 there is provided a pinion 40 which is rotatably fixed on the door 2 and has a shaft 41 fixed to the pinion 40 itself one end of the wire 29 is connected with the shaft 41 there is also provided a curved rack 42 which has a center identical with that of the door 2 so that it can engage with the pinion 40 the thin metal strip 5 is the same member as used in the above embodiment i e it is wound around the reel not shown by the self winding force thereof when the door 2 is closed when the door 2 is opened the pinion 40 which engages with the rack 42 rotates in response to the turning of the rack 42 in a direction shown z therefore the shaft 41 retracts the wire 29 to rotate the reel so that the strip 5 may be.