PURPOSE: To enable operation automatically and continuously, by a method wherein a plastic base material is molded into a predetermined form by preheating the same, which is stuck to a skin material sheet to which an adhesive agent has been applied, with pressure by superposing upon the skin material sheet and then the skin material sheet is cut off.

CONSTITUTION: A plastic base material P3 is preheated at a predetermined temperature with a preheating device 4, fed to an inlet side of a transfer molding device 5 and introduced into a molding stage 5-1 through feed, lowering and release actions of a feed bar 5e. An application roller 9c coming into contact with a skin material sheet L2 is turned and an adhesive agent 8 within an adhesive agent holding vessel 9a is applied to the surface of the skin material sheet L2 through an application roller 9c. The plastic base material P3 to be introduced onto a bottom force 5a' is set up onto the skin material sheet L2 set up to the bottom force 5a', which is pressurized by lowering a top force 5b'. With this construction, the skin sheet L2 is stuck to the undersurface of the plastic base material P3 and a tip side and middle part are cut off with a mold blade 5d'.