An airbag apparatus is provided in which constraint of a rider in case of front collision is achieved. In one form, an airbag apparatus to be mounted to a motorcycle includes an airbag which is deployed and inflated in case of front collision of a vehicle. The airbag forms a constraining surface for constraining a rider when deployed and inflated, and is configured to be deployed and inflated while extending the constraining surface along the direction connecting the abdominal portion and the chest portion of the rider when constraining the rider.