[Problem] To suitably control the deployment shape of an airbag, thereby improving the capability to restrain an occupant. Also, to reduce injury to an occupant approaching the steering wheel or instrument panel. [Solution] An airbag device according to the present invention comprises: a gas generator that generates expansion gas; an airbag that expands and deploys due to the expansion gas, thereby restraining an occupant; and a diffuser provided inside the airbag, the diffuser controlling the flow of the expansion gas. The diffuser comprises: a receiving surface disposed between the gas generator and the airbag in a first direction, where the first direction is the direction toward the occupant, the receiving surface receiving the expansion gas discharged from the gas generator; and a plurality of belt-shaped connecting members, one end of each of which is connected to an edge of the receiving surface, and the other end of which is directly or indirectly connected to the gas generator.