Airbag apparatus

To provide a development technology of an airbag apparatus which can ensure protection of a head portion and a breast portion of a vehicle passenger in case of vehicle accident. The airbag apparatus is configured in such a manner that a thickness of a head chamber 120 of a deployed and inflated airbag 102 in the lateral direction becomes larger than the thickness of a breast chamber 110 in the lateral direction in case of vehicle accident (Fig. 1).