The present invention provides a seat belt system comprising: a moving element (36) rotatably received in a housing (26); a device (32) for applying a pressurized gas to the moving element (36) when abrupt deceleration occurs on a vehicle; a tensile member (40) responsive to movement of the moving element (36) extruded due to the pressurized gas to generate a rotational torque; and a clutch mechanism (44) for transmitting the rotational torque generated by the tensile member (40) to a retractor shaft (24) to rotate the shaft (24) in a webbing-winding direction.