An airbag has a front panel positioned on an occupant side when inflated, and a rear panel of substantially the same shape as the front panel positioned on an opposite side to the occupant. Furthermore, an inflation restricting section, which restricts the inflated shape of the airbag, is formed by drawing together and fixing a portion of the front panel. When the airbag is inflated, the occupant side of the airbag is pulled inwards, thereby forming a cavity on the occupant side.