PURPOSE: To improve an adhesive strength of a surface fastener to a foamed molded form.

CONSTITUTION: A flexible maternal 12 integrated with surface fasteners 10 is set in a recess 22 of a mold 20, and an inner protrusion end 24A of an undercut part 24 is intruded into a side face 12A of the material 12. Then, liquid foamed plastic material 28 is transferred to the mold 20 and foamed in the mold 20. Thus, it can prevent the material 28 from being adhered to an engaging surface 10B of the fastener 10, and the face 12A and a rear surface 12C except a surface 12B of the material 12 coupled with the fastener 10 can be impregnated with the material 28.