An air bag inflation gas generator to feed combustion gas for inflation of air bags such as air gas for absorbing collision shocks, life jackets, rafts and escape chutes, that aim to easily and surely control the flow rate of combustion gas into the air bag at the initial inflation of the air bag and to effectively utilize the entire purifying filter. The generator has a longitudinal outer cylindrical member having a plurality of gas outlets in its outer periphery, an inner cylindrical member inserted in the outer cylindrical member having gas flow openings formed in the outer periphery, a final filter disposed between the outer cylindrical member and the inner cylindrical member, a plurality of gas generating agents accommodated in a laminated state in the axial direction of the inner cylindrical member having a through hole formed at the center, and an igniter and an ignition agent disposed at one end of the inner cylindrical member and a shielding member for shielding the through hole is disposed at the gas generating agent or between the gas generating agents disposed at the middle part of the inner cylindrical member. This invention forms a plurality of gas flow openings in the substantial part of the outer periphery of the inner cylindrical member, and the hole area of these gas flow openings are designed to be larger as they get a way from the gas outlets of the outer cylindrical member.