An airbag device to be mounted on a vehicle, comprising: an airbag that is formed in a bag shape to deploy by being supplied with gas, the airbag including a neck portion through which the gas is supplied, and a head facing portion that is located upward of the neck portion and that faces a head of an occupant of the vehicle when the airbag deploys and expands; and vent holes (81, 82) that are provided in the airbag, wherein the airbag has a bag shape of which a width that is a lateral direction of the vehicle is increased gradually from the neck portion toward a top of the airbag and a maximum width portion forms a head facing portion; and an area downward of the head facing portion is partitioned at intervals in a width direction into a plurality of pillar-shaped gas chambers (53, 54, 55) that are extended from the neck portion toward the head facing portion and that are spaced from each other in the width direction of the airbag, wherein the plurality of pillar-shaped gas chambers (53, 54, 55) comprises a central gas chamber arranged in a center in the width direction and formed in a shape which extends toward a widthwise center of the head facing portion, gas chambers (53, 55) except for the central gas chamber are arranged outside the central gas chamber outwardly away from the central gas chamber in the width direction, and the vent holes (81, 82) have at least one upper vent hole and at least one lower vent hole, wherein above the head facing portion, the upper vent hole is placed outside in the width direction with respect to a line extending in an extending direction of the central gas chamber and is placed inside in the width direction with respect to a line extending in an extending direction of each of the gas chambers (53, 55) arranged outside in the width direction, and is opened to the occupant of the vehicle and below the upper vent hole, the lower vent hole is placed at entrances of gas in the gas chambers (53, 55) except for the central gas chamber and is opened to an opposite side of the occupant of the vehicle. an airbag that is formed in a bag shape to deploy by being supplied with gas, the airbag including a neck portion through which the gas is supplied, and a head facing portion that is located upward of the neck portion and that faces a head of an occupant of the vehicle when the airbag deploys and expands; and vent holes (81, 82) that are provided in the airbag, wherein the airbag has a bag shape of which a width that is a lateral direction of the vehicle is increased gradually from the neck portion toward a top of the airbag and a maximum width portion forms a head facing portion; and a width that is a lateral direction of the vehicle is increased gradually from the neck portion toward a top of the airbag and a maximum width portion forms a head facing portion; and an area downward of the head facing portion is partitioned at intervals in a width direction into a plurality of pillar-shaped gas chambers (53, 54, 55) that are extended from the neck portion toward the head facing portion and that are spaced from each other in the width direction of the airbag, wherein the plurality of pillar-shaped gas chambers (53, 54, 55) comprises a central gas chamber arranged in a center in the width direction and formed in a shape which extends toward a widthwise center of the head facing portion, gas chambers (53, 55) except for the central gas chamber are arranged outside the central gas chamber outwardly away from the central gas chamber in the width direction, and the vent holes (81, 82) have at least one upper vent hole and at least one lower vent hole, wherein above the head facing portion, the upper vent hole is placed outside in the width direction with respect to a line extending in an extending direction of the central gas chamber and is placed inside in the width direction with respect to a line extending in an extending direction of each of the gas chambers (53, 55) arranged outside in the width direction, and is opened to the occupant of the vehicle and below the upper vent hole, the lower vent hole is placed at entrances of gas in the gas chambers (53, 55) except for the central gas chamber and is opened to an opposite side of the occupant of the vehicle.