To prevent outward gas leakage between the airbag cushion and inflator during expansion and deployment with a simple configuration. The present invention provides an airbag device including: an airbag cushion having at least two panels; an inflator that discharges gas inside the airbag cushion; a first piece extending from an edge of a first panel of the two panels that is folded in the middle into the airbag cushion; a second piece provided on a portion near the edge of a second panel facing the first piece inside the airbag cushion and sewn to the folded part of the folded first piece; and an insertion passage for the inflator formed from sewing the folded part and the second piece, and extending from inside the airbag cushion to outside.