Airbag apparatus for side collision

In order to provide an airbag apparatus for side collision in which a gas pressure in a lower chamber (1a) can be maintained at a high level for a sufficiently long time, an airbag (1) is formed by making a sheet material such as cloth or resin sheet into a bag shape, and the interior thereof is divided by a seam (2) into the lower chamber (1a) on the lower side and an upper chamber (1b) on the upper side.