To provide an airbag device for side impact in which a folding shape of the airbag can be made compact and the airbag can be developed fast in a vertical direction at the time of development and expansion.

An airbag device for side impact comprises an airbag 15 that is folded from an occupant side wall 16 and a vehicle body side wall 17 having the substantially same outer shape to each other through an upward or downward shrinkage folding step. During the upward or downward shrinkage folding step, a lower end 15b is formed with a folding location 27 to cause a part of the occupant side wall 16 and the vehicle body side wall 17 to be inserted into the airbag 15. The folding location 27 is constituted of a body 28 formed by inserting the part of the occupant side wall 16 and the vehicle body side wall 17 into the airbag 15, and a protrusion location 29 protruded downward from the body 28. The airbag 15 is folded by folding back the protrusive location 29 in such a way that it may be arranged at a vehicle outside part of the body 28.