An airbag device includes an airbag, a case in which the folded airbag is housed, and an airbag cover that covers the folded airbag. An attachment portion of the airbag cover is attached to a peripheral wall portion of the case by a rivet being caused to pass through. The case is such that a vicinity of a boundary region between the peripheral wall portion and a bottom wall portion is curved in an approximate arc in cross-section. The attachment portion includes a protruding portion that protrudes toward the peripheral wall portion side in an end edge farther to a leading end side than a region of penetration of the rivet. The protruding portion is disposed in a position opposing a curved region configuring a boundary region between the peripheral wall portion and the bottom wall portion, and is protruded in such a way as to be oriented farther to a central side of the bottom wall portion than an outer side face of the peripheral wall portion, and an edge on the peripheral wall portion side of a protruding end face is disposed in a state of non-contact with the curved region.