A seat back pad 70 has a groove 73 for tucking a skin material therein, formed at borders between a central portion 71 and side portions 72. A hole (slot hole 74) is formed in a bottom of the groove 73 along the groove 73. A tuck-in wire 76 for tucking the skin material in includes a plurality of tuck-in portions 76A provided along the groove 73, and a connecting portion (detour portion 76B) detouring around the hole and connecting the tuck-in portions 76A. With this configuration, when an upper body of an occupant P subsides into a seat back S2 in a rear-end collision of a vehicle, the central portion 71, defined by the groove 73 as a border, is easily and sufficiently moved rearward relative to the left and right side portions 72. Furthermore, the tuck-in wire 76 is not exposed through the hole, and thus adhesion between the seat back pad 70 and the tuck-in wire 76 can be improved.