Airbag device

An airbag device, the airbag device comprising:

• an airbag that expands and deploys to integrally cover the head and side sections of an occupant seated in a vehicle seat;
• and
• an inflator that supplies gas to the airbag,
• wherein the airbag includes:
• a head protecting chamber that covers the head of the occupant and side protecting chambers that cover the side sections of the occupant when the airbag is in an expansion completed state where expansion and deployment are completed;
• and
• in a state where the airbag is stowed rolled in a roll shape or folded in a bellows shape, and stowed in a backrest of the vehicle seat from a first side to a second side over a top part, there is an additional folding part extending from the outer periphery of the attachment end side of the stowed airbag to the backrest, where the additional folding part is provided covering at least a portion of the rear side of the stowed airbag that is rolled in a roll shape or folded in a bellows shape,
• wherein a free end of the additional folding part is secured directly to a top-most exterior surface of the vehicle seat.