PURPOSE:To improve dimensional accuracy after joining and to improve joint strength by using a foil-shaped brazing filler metal for Al or Al alloy brazing manufactured by a quick cooling method using liquid. CONSTITUTION:A melt having a prescribed compsn. is quickly cooled at a prescribed speed on a quick cooling roll under rotation, by which continuous foil is obtd. instantaneously. The Al-base foil-shaped brazing filler metal obtd. by such method is a uniform solid soln. of Al having extremely fine crystal grains and excellent ductility. Diffusion welding by melting is easily made possible by interposing such foil-shaped brazing material between the joint surfaces in the stage of interposing said materials between joining parts consisting of Al or Al alloy and subjecting the parts to diffusion joining by melting.