PROBLEM TO BE SOLVED: To promote reutilization by separating a gas ejecting means such as a gas generating agent from an inflator. SOLUTION: Notches 44 are formed at the prescribed portions of the upper case 12 and the lower case 14 of an inflator 10 (directly above and directly below a gas generating agent storage chamber 26) respectively. Rigidity is reduced at the portions formed with the notches 44 on the upper case 12 and the lower case 14, and these portions are made fragile. The gas generating agent 28 can be separated from the inflator 10 before the reutilization process is started. The reutilization of the inflator 10 can be promoted.