An airbag and an airbag device allowing the airbag to stably stand by itself are provided. The airbag is usually folded and embedded in an instrument panel, and in an emergency, a gas is supplied to inflate and expand the airbag between a windshield and a passenger. Also, the airbag includes a front inflation portion inflating toward a windshield side, and a back inflation portion inflating toward a passenger side. The front inflation portion includes a bottom portion pressed against a surface of the instrument panel at a time of an inflation and expansion; and a front face portion which projects to the windshield side in a projecting shape.