To prevent the occurrence of yellowing of oxide film by forming an oxide film composed essentially of aluminum oxide on the surface of a member made of aluminum-base alloy containing specific amounts of Si and constituting this oxide film of a porous inner layer and a surface layer denser than the inner layer.

An oxide film composed essentially of aluminum oxide is formed on the surface of a member made of aluminum-base alloy containing 7.5-18 wt.% Si. This oxide layer consists of a porous inner layer and a surface layer denser than the inner layer, and the porosity of the outer layer and that of the inner layer are regulated to ≤30 vol.% and >30-50 vol.%, respectively. Further, the thickness of the outer layer and that of the inner layer are regulated to 0.06-0.3 μm and 3-70 μm, respectively, and the surface of the aluminum- base alloy member is subjected to boehmite treatment and then to anodic oxidation treatment in a solution containing sulfuric acid, oxalic acid, phosphoric acid, or the like. By this method, the oxide film capable of keeping dimensional accuracy and having uniform dark gray color can be formed.