PURPOSE: To prevent dirt of a surface material by sticking one end of a first film to the terminal of a first skin material and pulling out the other end to the outside of a lower mold and sticking a second film on the surface of a second skid material provided to an upper mold and filling foaming resin.

CONSTITUTION: A first skin material 18 with a first film 21 stuck thereto is arranged to a lower mold 12. Further a second skin material 19 with a second film 22 stuck thereto is arranged to an upper mold 13. Then both a headrest frame 27 and a stay 25 are inserted into the lower mold 12 and the upper mold is matched with the lower mold. In this case, the second film 22 is lapped on the first film 21 so as to intrude the second film 22 into the lower mold 12. The raw liquid 28 of introduced foaming synthetic resin is not almost leaked to the outside by the overlapped films 21, 22.