PURPOSE: To raise production efficiency as the heating of a resin sheet before press molding is not necessary, by extruding a resin base material into sheet form, and by press molding it superposed by a skin member before the hardening of the resin sheet.

CONSTITUTION: A molten resin material constituting a base material 12 is continuously extruded through a die 18 by an extruding machine 16. Thereby a resin sheet 20 in strip form is formed, and a skin member 22 wound in roll form near the extruding machine 16 is drawn out. Before the resin sheet 20 is hardened, the resin sheet 20 and the skin member 22 are continuously superposed by nipping between a pair of rollers 24, 24. Here the skin member 22 which constitutes a skin 14 is a flexible sheet of polyvinyl chloride etc. backed with a knitted cloth. The superposed resin sheet 20 and skin member 22 are forwarded continuously from rollers 24, 24 to the direction showed with an arrow A, and press molded by a press machine 28 before the resin sheet 20 is hardened.