To prevent the rubbing sounds, damage, etc., caused by friction between seat pads and tension springs by using a laminated material formed by integrally joining a staple fiber web and a woven fabric as a backing material, joining an expansion foam body to this staple fiber web and expansion foaming the set pad integrally with the backing terminal from a foamed resin.

The laminated material formed by integrally joining the staple fiber web 11a to the woven fabric 11b consisting of tape yarn by means of needle punching is used for the backing material 11. Such backing material 11 is used and is assembled and arranged within molds by directing the fluffing side by the short fiber web toward a cavity space and the foamed resin, such as foamed urethane, is injected into the molds and the expansion foamed body 10 is expansion molded integrally with the staple fiber web, by which the formation as the back pad 1 with the backing material by the expansion forming mold is made possible. The back pad 1 with the backing material is assembled to a seat back frame 2 and is supported from behind by a zigzag spring 3, by which the back pad is assembled as the seat back of the seat for automobiles.