To provide an airbag device for side collision capable of obtaining a predetermined reaction force by inflating a waist chamber at an initial stage of actuation, and then inflating a chest chamber, so as to entirely obtain a good deploying performance.

This device comprises a waist chamber 16b positioned at a bottom, a brlly chamber 16c positioned at a middle, and a chest chamber 16d positioned at a top blocked by a non-expansion part 16a, and an inflator chamber 16e positioned at a middle on a folded side. The bottom of the inflator chamber 16e is communicated with the folded side top of the waist chamber 16b. The waist chamber 16b is communicated with the brlly chamber 16c through a first narrow passage 16f, and the brlly chamber 16c is communicated with the chest chamber 16d through a second narrow passage 16g.