An easily manufacturable airbag and airbag apparatus having such an airbag are provided in which the inflated shape of the airbag is regulated by panels in place of tether belts. The airbag comprises a first panel surrounding a first vacant chamber and a second panel surrounding a second vacant chamber. When manufacturing the airbag, confronting surfaces of panels are placed one on top of the other, and intermediate sections are connected thereto by sewing. Then, peripheral edges are superposed and connected by sewing. Finally, both ends in the extending direction of the peripheral edges are connected together by sewing. The airbag is manufactured by such a procedure. A tether panel is composed by placing confronting surfaces and one on top of the other. A vent port for ensuring communication between vacant chamber and is provided in the tether panel.