The present invention is to achieve effective utilization of a space for a seat and in the periphery thereof by arranging a gas generator in a vacant space around the seat, an inflatable seat bag (10) is arranged above a seat pan (5). A seat cushion is installed above the seat bag (10). A gas introduction port is provided at a longitudinal end (the side of a side frame (1a)) of the seat bag (10), and a gas supply duct (12) from a manifold (22) at a distal end of an inflator (20) is connected to the gas introduction port. The gas supply duct (12) is disposed along the lower side of an S-spring (1s). The inflator (20) is mounted to a spindle (2) with a bracket (21). A distal end of a gas introduction duct (36) is connected to an end portion of a lap bag (35) on the side of an anchor (32). A proximal end of the duct (36) is connected to another gas outlet of the manifold (22). |