An airbag device includes an airbag, an inflator and a retainer. The retainer includes a generally tubular holding section for holding the inflator therein and mounting means which protrudes out of the holding section in a direction generally perpendicular to an axis of the inflator to be mounted on a vehicle body member in order to mount the airbag and the inflator on the vehicle body member. The holding section includes an elastically deformable support region which has been elastically deformed and brought into abutment against an outer circumference of the inflator when the inflator was inserted into the holding section, and supports the inflator in the elastically deformed state at an inner side of the holding section, and a supporting projection which has higher rigidity than the elastically deformable support region and abuts against the outer circumference of the inflator at the inner side of the holding section.