An airbag device includes an airbag, an inflator, a retainer and an airbag cover. The airbag is usually folded, and expands and develops in an emergency. The inflator supplies gas to the airbag. The retainer secures the airbag and the inflator. The airbag cover houses the airbag. The airbag cover has a plate-like part and an inner case. The plate-like part constitutes the interior surface of a vehicle. The inner case is disposed on the rear surface of the plate-like part and constitutes an expansion and development path for the airbag. The inner case has a plurality of retaining holes for retaining the retainer. The retainer has a roughly planar-shaped support body capable of being stored within the inner case and an annular belt-like body inserted into the retaining holes and attached to the support body.