An air belt apparatus that can reduce the required tolerance level of a pipe is provided. Gas supplied from an inflator 12 flows into a bag body 16 through a pipe 18 so as to inflate a lap bag 15. The inflator 12 is connected to a gas inlet 16a of the bag body 16 via the pipe 18. The gas inlet 16a is cylindrical, and the pipe 18 is inserted in this cylindrical gas inlet 16a so as to extend beyond an inner end of the gas inlet 16a.