To fix the flux powder and the brazing filler metal powder on an aluminum extruded stock with excellent productivity at a low cost by melting the thermoplastic resin making use of the heat of the aluminum extruded stock immediately after extrusion, and using a molten layer as a binder to fix the flux powder and the brazing filler metal powder.

An aluminum extruded stock is heated around 500-600°C immediately after the extrusion. While it still keeps sufficiently excessive heat and its temperature is higher than the melting point of the applicable thermoplastic resin, the thermoplastic resin powder such as butylene-acrylic acid ester or methacrylic acid ester copolymer is applied and adhered thereto. The adhered resin is melted to wet the surface of the aluminum extruded stock, and a molten layer is formed on the surface to be brazed of the extruded stock, and the molten layer becomes the binder.