PURPOSE: To protect the surface of a metal plate and a molding die from damage by retaining the metal plate pressed on the die through an elastic member to prevent penetration of melted resin to the surface thereof during the injection molding.

CONSTITUTION: A metal plate 3 is placed on a lower die 2 with the surface thereof laid on the molding surface 2a thereof 2 and retained pressed on the molding surface 2a of the lower die 2 with elastic members 4, 4... by an upper die 1 when the upper die 1 and the lower die 2 are clamped. The pressing force per one elastic member 4 is preferably 5W10kg/cm2 and the pressing area 1W 3cm2. Then, a melted resin is injected into a molding spece 7 to mold a resin layer 8 integral on the back of the metal plate 3 having the elastic member internally chilled. The interval (d) between the elastic members 4, 4... shall be about 20cm.