PURPOSE: To provide a method for attaching an inflator to an air bag case, which can improve the workability of attachment of an inflator to an air bag case.

CONSTITUTION: After installing a bag body 14 under the folded condition inside of an air bag case 12, a nozzle cap 30 is fitted out of one axial end part 16a of an inflator 16, and the inflator 16 is inserted to a through hole 20 of one side under this condition. After inserting the inflator 16 for arrangement, the nozzle cap 30 is removed from the inflator 16. Consequently, at the time of inserting the inflator 16, the peripheral surface 30A of the nozzle cap 30 pushes the end part 14A of the bag body 14 under the folded condition to go backward, and the inflator 16 is inserted. Consequently, the workability of attachment can be improved.