AIRBAG DEVICE AND METHOD FOR INFLATING AIRBAG DEVICE

An airbag device includes a gas generator including a first gas generating agent and an ignition unit, and an airbag configured to inflate upon receiving a combustion gas from the gas generator, the airbag including an inlet being configured to cause the combustion gas supplied from the gas generator to flow into an internal space of the airbag, a bag-shaped portion configured to separate, from an outside, the internal space into which the combustion gas flows from the inlet, the bag-shaped portion being configured to be in a folded state and to be in an inflated state by receiving the supply of the combustion gas, and a second gas generating agent that is disposed at a predetermined position on an inner surface of the bag-shaped portion and generates gas by using thermal energy of the combustion gas without accompanying a combustion reaction.