AIRBAG DEVICE AND PASSENGER PROTECTION DEVICE

An airbag device includes an airbag that is supplied with gas generated by an inflator during a vehicle collision, and that inflates and deploys from a rear side of a vehicle seat toward a front side via an upper side. In an inflated and deployed state, the airbag includes a pair of front-rear chambers extending in a seat front-rear direction via left and right sides of a head of a passenger, an airbag body that is communicated with the pair of front-rear chambers and that is disposed at a front side of the passenger between the pair of front-rear chambers, and an auxiliary chamber into which gas inside the airbag body flows indirectly at least during restraint of the passenger by the airbag body.