NOVELTY - An amorphous-silicon layer (2) is formed on the substrate (1), and a metal layer (3) is formed on the amorphous-silicon layer. The metal layer contain metal which carries out eutectic reaction with the silicon contained in the amorphous-silicon layer. Then, the amorphous-silicon layer and metal layer are heated, such that silicon contained in the amorphous-silicon layer is turned into solid solution. Thus, the solid solution in metal layer is crystallized, to form polycrystalline-silicon layer (4). Thus, manufacture of polycrystalline-silicon thin film is enabled.    USE - Manufacture of polycrystalline-silicon thin film is used for manufacture of thin-film substrate used for solar cell.    ADVANTAGE - The polycrystalline-silicon thin film-type solar cell comprising thin film substrate has improved conversion efficiency.    DETAILED DESCRIPTION - An amorphous-silicon layer is formed on the substrate, and a metal layer is formed on the amorphous-silicon layer. The metal layer contain metal which carries out eutectic reaction with the silicon contained in the amorphous-silicon layer. Then, the amorphous-silicon layer and metal layer are heated, such that silicon contained in the amorphous-silicon layer is turned into solid solution in metal layer. Thus, the solid solution in the metal layer is crystallized, to form polycrystalline-silicon layer on metal layer. Thus, manufacture of polycrystalline-silicon thin film is enabled. The thin metal layer is exposed to oxygen or air, to form a thin layer of metal natural-oxidation film. The metal contained in the metal layer is chosen from aluminum, titanium, nickel, tin, and indium. The amorphous-silicon layer is silicon-germanium compound layer.    DESCRIPTION OF DRAWING(S) - The drawing shows the explanatory illustrating manufacturing method of polycrystalline-silicon thin film. (Drawing includes non-English language text)    Substrate (1)    Amorphous-silicon layer (2)    Metal layer (3)    Polycrystalline-silicon (4)    Polycrystalline-silicon thin film substrate (40)