A configuration of the airbag module according to the present invention is an airbag module including an airbag cushion that is folded or wound, an inflator equipped in the airbag cushion, and a case-shaped housing where the airbag cushion is stowed. Herein, the housing includes four side walls, the upper part thereof being open; one side wall of the four side walls and two side walls positioned and connected on both sides thereof; and two extendable walls and at the opening above the four side walls that are in a folded state prior to expansion and deployment of the airbag cushion and open up when the airbag cushion expands and deploys.