PROBLEM TO BE SOLVED: To provide a reduced weight and to easily assembling an air bag and an inflator. SOLUTION: A side air bag device M1 comprises an air bag 11 and an inflator 18. The air bag 11 is folded in an upper part than a belt line BL in the periphery of the door opening W of a car inside and formed to be a bag made of cloth developed to cover the door opening W during expansion. The inflator 18 is disposed in the lower side of the belt line BL in the periphery of the door opening W and supplies gas for expansion to the air bag 11. A gas flow-in part 14 roughly cylindrical in shape is formed in the lower part of the end side of the air bag 11. The gas flow-in part 14 is extended to the lower side of the belt line BL and connected by being exterior packaged on the outer peripheral surface of the inflator 18.
