PURPOSE: To contrive to obtain a strong bond at reduced processes by a method in which the structure having the section in which metallic sheet, adhesive and the core member of a sandwich structure are piled in order thereof is formed, and yet te forming of the core member and also the integrally forming for the metallic sheet and the core member are achieved at once at the core forming stage.

CONSTITUTION: The metallic sheet 1 wound around an uncoiler 30 is sent to a forming machine 32 and formed into a trough shape. Next, the bottom surface of the trough is coated with about 10μm thickness of opoxy resin by a roller. Then, a sheet like member 4 is guided and stuck to this adhesive 2 by way of a guide 34a. Next, phenol foam stock 6a is injectd to the trough surface by a spray gun. A sheet like material 5 (backing material) is lapped onto the foam being in foaming stage. Said materials are sent to a heating and pressurizing device 39, and the foam therein is completely foamed during its passage through said device 39, and then the adhesive is also dried completely. The plate like composite plate is delivered from an exit, and is cut into the dimension of 10 shaku or 12 shaku, etc. Thus, the composite panel may be formed.