A method for anodizing aluminum, wherein an object (29) made of aluminum or an aluminum alloy is anodized in an electrolytic solution (25), and thereby an anodized aluminum film is formed on a surface of the object (29), is provided. The electrolytic solution (25) is comprised of at least one acid selected from organic acids having two or more carboxylic groups, moves at an average speed of 15 cm/sec or less along at least an outer surface of the object (29). The anodization is performed under conditions that a temperature of the outer surface of the object (29) is 80° C. or less, and current density is in a range from 10 to 170 A/dm2.