An airbag includes a tab that is inserted into and supported by a substantially flat-plate-shaped bracket disposed on a vehicle. The tab has a first slit extending along a direction substantially orthogonal to a direction of inflation and deployment of the airbag in plan view. The first slit allows insertion of the bracket in a normal time. The tab further has a second slit opening into a point at one end portion or on an intermediate portion of the first slit at an angle intersecting with the first slit in plan view.