VEHICLE SEAT PROVIDED WITH SIDE AIRBAG DEVICE

Initial occupant restraint performance of a side airbag can be enhanced whilst also achieving a reduction in costs. A seat back board (16) made from resin is fitted to side frames (26) of a seatback frame (14) from a seat rear side. A seat width direction outer side side portion of the seat back board (16) is integrally formed with a case portion (102) that houses a side airbag device (100) that is fixed to an outside face of the side frame (26). The presence of a side wall portion (102B) of the case portion (102) suppresses a side airbag (106) from expanding towards the seatback outside in a ball shape during initial inflation.