The present invention provides a method for forming an anode oxide film, in which on the assumption that a direct-current power source is used, a thick anode oxide film can be formed with good productivity within a short time without using special equipment. The method further includes annealing the main conductor layer by directing light from an array of continuous wave lasers into a line of light extending at least partially across the thin film structure, and translating the line of light relative to the thin film structure in a direction transverse to the line of light. The hydraulic fluid preferably contains no glycols in some embodiments.