A seat configuration member and a vehicle seat employing the seat configuration member are provided that are capable of covering reclining mechanism components and maintaining a high quality external appearance of the vehicle seat, and are moreover capable of achieving a reduction in the number of components. A lower side coupling and fixing portion (50) disposed on a seat width direction outer side of a seat back board (16) that is made from resin is integrally formed with an attachment portion (102) that is L-shaped in plan view. A side airbag device (100) is attached to a horizontal wall portion (122) of the attachment portion (102). A seatback pad and a cover are mounted to the seat back board (16) configured as described above, and the seat back board (16) is assembled to side frames (26) of a seatback frame (14).