PURPOSE: To enable minimizing, by providing a tension belt between a drive roller to rotate normally and reversely interlocking the door opening and shutting and a driven roller being pinched, minimizing winding force of the retractor of binding belt and reducing feeling of binding.
CONSTITUTION: A tension belt 6 is sewed to fix at the middle of lap belt 2, another end of the tension belt 6 is fixed to the shaft of retractor 8 on the front portion of the room. One end of the lap belt 2 is installed the emergency lock type retractor 4 of the door 3. The tension belt 6 is pinched between the drive roller 12 driven by a motor 10 to rotate normally and reversely linking the door 3 opening and shutting and the driven roller 13. Thus, since winding in and out of the tension belt can be carried out by slight force, use of small sized motor enables, minimizing installation space and winding force of the retractor 4 of lap belt 2, driver's feeling of binding can be reduced.