Abstract: This invention offers a method for forming a resin composite material, containing the steps of: (1) treating the surface of a carrier resin to treatment introduce ion exchange groups, (2) introducing metal ions to treat the carrier resin surface by treating the surface of said carrier resin with a solution containing metal ions, (3) converting said metal ions to a component containing a metal element, (4) forming a metal foil on top of said component containing a metal element, and (5) transferring said metal foil to a resin substrate by heating said metal foil. This method provides a carrier resin substrate having a metal foil of any desired thickness laminated or cast onto it. In this way a carrier resin containing a metal foil, particularly a copper foil, having a thickness, such as 8 ?m or less, can be prepared that is otherwise difficult to prepare using conventional methods.