The side airbag device is installed in a seat in the vehicle. It has an airbag unit (21) containing an inflation device and a folded airbag in an airbag housing (22), which is fitted to one side of the centre of the seat relative to, and in close proximity to, a frame member (13). This frame member extends along a side sector of the seat. The aperture of the airbag housing is thus pointed in a specific direction. The airbag housing is attached to the frame member by a clamping frame. The frame member may include a tubular frame extending in and along either side of the seat.
