An airbag device includes a door (16), an inflator (18), and an airbag (20). The door (16), provided in a vehicle-body outer panel (12), is opened to open an opening (12A) in the vehicle-body outer panel (12) when a predetermined situation occurs. The inflator (18) is disposed inside the door (16). The inflator (18) includes a gas-injection port (36) that is closer to the end (16B) of the door (16) in the longitudinal direction of the door (16) than to the center of the door (16) in the longitudinal direction of the door (16). The airbag (20) is disposed at a predetermined position inside the vehicle-body outer panel (12). When the predetermined situation occurs, the airbag (20) is inflated by the pressure of the gas supplied from the inflator (18) to open the door (16), and the airbag (20) passes through the opening (12A) in the vehicle-body outer panel (12), and is deployed toward the outside of a vehicle body. The high inflation pressure of the airbag (20) is applied to the end (16B) of the door (16).