PURPOSE: To prevent blowing gas and the like from leaking through stay inserting holes and check the proceeding of impregnation of the stock liquid of foaming synthetic resin so as to be felt good by a method wherein stay covers are coveringly fitted to headrest stays, each of which is inserted in each stay inserting hole, so as to be brought into close contact with a top force side by means of blowing pressure at the foam molding of padding material.

CONSTITUTION: Firstly, the tubular part 32 of each stay cover 31 is inserted in each stay inserting hole 13a of a top force 13. The terminal 25 of a skin material 24 is pinched between the pressing part 33 of the stay cover 31 and the top force 13. Next, the top force 13 is registered to a bottom force 12 so as to pour stock liquid of foaming synthetic resin from an inlet 15 so as to foam-mold padding material integral with the skin material 24 and a headrest frame 21. The pressing part 33 of the stay cover 31 is pressed against the under surface of the top force 13 and the side part of the bottom force 12 by the blowing pressure developing at foam molding and the stay inserting hole 13a is sealed by the pressing part 33 and the tubular part 32. Accordingly, the padding material 23 can be molded under the desired blowing pressure. Further, the impregnation of the stock liquid of the foaming synthetic resin between the rear face of the terminal 25 of the skin material 24 and the pressing part 33 and the leakage of blowing gas through the gap between said rear face and the pressing part 33 can be prevented from occurring.