Airbag device

An airbag includes two base cloths (36,37) sewn together at their outer peripheries by a seam (39) extending from a central portion to the outer periphery of the base cloths (36,37) into a vortical shape. When gas is supplied from an inflator (31) to a center aperture (37a) of one of the base cloths (36,37) to inflate the airbag (32), load generated by gas pressure breaks the seam (39) sequentially from the central portion to the outer periphery, preventing sudder deployment of the airbag in fore and aft directions at the initial stage of deployment, thereby enabling not only soft restraining of passengers but also sufficient restraining by deploying the airbag (32) into a final shape that is flat in fore and aft directions upon completion of breaking the seam (39).