Abstract: In an air bag apparatus which is installed at an opening of a dashboard, a case fixed to a vehicle dashboard has an opening and side walls having through holes. A door to cover the opening of the case has connecting portions having through holes. The connecting portions of the door are connected to the side walls of the case by stays. In this case, one end of each of the stays is fixed to the outer face of one of the side walls and the other end penetrates both the respective through holes of one of the side walls and one of the connecting portions so that the door can move in three dimensions with respect to the case. As a result, the door can be disposed at the opening of the dashboard without tilting with respect to the upper surface of the dashboard.