PURPOSE: To easily load and unload an insert, reduce manhours, and enhance a yield by a method wherein when an inner seal flange is set to a mold to be integrally molded with a core material of a door trim, lugs are provided on an insert of the mold, and cutouts to be fitted with the inserts are provided on a flange surface of the inner seal flange.

CONSTITUTION: Lugs 7 are provided on an insert 5 at appropriate intervals. The lugs 7 are fitted into cutouts 4 provided on a flange surface of an inner seal flange 3. Loading holes 8 are provided in a loading part 14 of a mold. It is preferable that a sliding device 17 for sliding the lugs 7 of the insert 5 is provided on an end part of an lower mold 11. The insert 5 combined with the inner seal flange 3 is fixed by inserting the lugs 7 of the insert 5 into the loading holes 8. A fiberglass reinforced hard urethane material or the like is injected to the lower mold 11, and the mold is closed. After foam molding, the mold is opened, and the lugs 7 of the insert 5 are slid by the sliding device 17 of the lower mold. In this manner, the inner seal flange 3 integrally molded with a core material 2 can be obtained.