SIDE AIRBAG DEVICE

The side airbag device is provided with a cushion, an inflator arranged on the occupant side of a side part of a seat frame, and a support plate, where the cushion in a folded state includes: a first portion positioned on the occupant side of the seat frame side part, and a second portion positioned on the side opposite the occupant side of the seat frame side part and wraps around the vehicle front side from the first portion to sandwich the seat frame side part together with the first portion; and the support plate includes: a main body part for supporting the second portion, and a rearward extending part, in which through-holes and are formed extending from the main body part toward the rear of the vehicle beyond the second portion for allowing stud bolts and of the inflator to pass through.