To provide a seat back carpet mounting structure capable of preventing the whole carpet from appearing levitated, precluding the carpet from being left in the turned-up condition, hindering flexible part(s) from deformation, and enhancing the appearance of the rear face of the seat back.

The carpet 13 is attached to boards 15 and secured to frames 12 of a left and a right seat back 11.... A space part 25 is formed at the adjoining side ends 15a of the left and right boards 15. The lateral edges 13a of the carpet 13 are included in winding to the rear surfaces of the boards in such a condition as protruding outward laterally from the side ends of the boards in such a way filling the space part 25, and cores 31 are sewn up to the lateral edges 13a of the carpet in their sewing parts 32 and fastened in winding by the edges 13a.