The invention relates to a method for forming a selective absorption surface of a heat collector using solar energy and a selective absorption processing film formed based on the method, and the selective absorption surface has good heat collection characteristics and is capable of being formed on a metal substrate. The method for forming the selective absorption surface is characterized in that the selective absorption surface is formed on the surface of the abovementioned metal substrate by impregnating the metal substrate in a chemical conversion treating fluid containing sulfuric acid and sodium dichromate or sulfuric acid and chromic anhydride, and the chemical conversion treating fluid contains a metal salt of oxyacid or a metal salt of haloid acid.
