The airbag apparatus includes an airbag folded and housed in a housing. The airbag includes an outer bag constituting an outer wall of the airbag and an inner bag disposed inside the outer bag. The inner bag includes an outlet port supplying inflation gas into the outer bag and an arm inflatable into a tapered bag contour. The arm holds down a peripheral defected region of the outer bag defected from the housing onto a top plane of a ring of a steering wheel all the while that the inner bag remains completely inflated at the operation of the airbag apparatus.