PURPOSE: To enhance the weldability of a reinforcing material with the material of other area and to achieve the enhancement of strength and wt. reduction by melting the reinforcing material consisting of a reinforcing fiber and a thermoplastic resin under heating and melting the reinforcing material and a compsn. consisting of a thermoplastic resin compatible with the thermoplastic resin of the reinforcing material and a reinforcing fiber to integrate both of them.

CONSTITUTION: A first reinforcing layer 13 consisting of a reinforcing fiber with a length of 5-100mm composed of an inorg. fiber such as a glass fiber, a metal fiber such as a stainless steel fiber or an org. fiber such as an aramide fiber and a thermoplastic resin such as polyethylene, polyvinyl chloride or polystyrene is formed and a second reinforcing layer 14 consisting of a continuous reinforcing fiber arranged in an almost one direction and a thermoplastic resin are laminated to form a reinforcing material and at least the surface of the first reinforcing layer 3 of the reinforcing material is heated and melted. At the same time, a compsn. consisting of a thermoplastic resin compatible with the thermoplastic resin of the first reinforcing layer 13, for example, polymethyl methacrylate or polyvinyl chloride and a reinforcing fiber is heated and melted to be supplied to the first reinforcing layer 13 to be integrated therewith.