Side airbag device

A side airbag device stored in a side support of a vehicle seat includes an airbag module having an airbag with first and second chambers and an inflator and a webbing partially covering the airbag module. The first chamber is deployed toward a front side of the side support and the second chamber accommodates the inflator therein and is deployed at an inner side with respect to the first chamber. The webbing extends from a rear side of the airbag module along an inner side surface of the airbag module, passes through a pad of the side support along a first path so as to reach an outside of the side support, and further extend along an outer surface of the side support and reach proximately a front edge of the side support when viewed in horizontal cross section of the airbag module from above.