To provide an air bag device capable of efficiently conducting a confirmation test for obtaining the optimum air bag device corresponding to kind of vehicle.

An air bag module 9 composed of an inflater 7 and an air bag body 8 is incorporated in a seat bag part 2. The air bag body 8 swelling by injection gas from the inflater when a vehicle collides on its side is arranged in a space between an occupant and an inner wall of a vehicle compartment. The air bag body 8 is sewn by overlapping an occupant side cloth part 8a and a cloth part 8b on an inner wall side of the vehicle compartment. A longitudinally sewn part 19 extending vertically at a front side position of the inflater and a laterally sewn part 17 extending toward the front from the inflater are formed in an overlapping part 800 of both cloth parts. An upper side chamber 16 is formed on a front side of the longitudinally sewn part 19 on an upper side of the laterally sewn part 17, and a lower side chamber 15 is formed on a lower side of the laterally sewn part 17. A communicating part 18 for leading injection gas into the upper side chamber from the lower side chamber is formed on a tip side of the laterally sewn part.