There is provided an alkaline cleaning of aluminum alloy, in which the attained corrosion resistance is equal or superior to the acidic cleaning agent, and which mitigates the disadvantages of the acidic cleaning agent, such as corrosion of plant, processing of the waste liquid, and energy cost, and which attains improved productivity.The cleaning liquid from 0.5 to 40 g/L in total of one or more alkali builders selected from alkali metal hydroxide, alkali metal carbonate, inorganic alkali metal phosphate and alkali metal silicate, from 0.2 to 10 g/L of one or more of organic phosphonic acid and its salt (A), from 0.001 to 2 g/L of one or more metallic ions (B) selected from metallic ions having from 5.0 to 14.0 of stability constant with the organic phosphonic acid and its salt, and from 0.1 to 10 g/L of surfactant. Particularly, the weight ratio of (A):(B) is in a range of from 100:0.05˜20.