To impart lubricity with durability to an anodically oxidized film by executing electrolysis in an aq. soln. of fatty esters after executing an anodically oxidizing treatment on aluminum.

At the time of executing a surface treatment of the anodically oxidized film of aluminum, the electrolysis is executed in the aq. soln. of the fatty esters after executing the anodically oxidizing treatment on the aluminum. And then, fatty acid is precipitated in the anodically oxidized film. A phosphide is precipitated in the anodically oxidized film by executing the electrolysis in the aq. soln. of the phosphide. The anodically oxidizing treatment is executed in the aq. soln. in which an inorg. acid such as sulfuric acid and chromic acid and an org. acid being an electrolyte are mixed by using aluminum to be treated as an anode and by using a lead alloy as a cathode in 1-4A/dm2 current density and -5 to 25°C temp. In this way, the surface treated aluminum having a film structure capable of maintaining a lubricating effect is obtained even if the film is weared.