PURPOSE: A nickel dissolution preventing method for an anodic oxide film sealed with nickel salt is provided to achieve desired effect through short-time treatment in tannin aqueous solution by controlling the concentration and temperature of the tannin aqueous solution. CONSTITUTION: A nickel dissolution preventing method for an anodic oxide film sealed with nickel salt comprises steps of: dipping the anodic oxide film in tannin aqueous solution which includes pH adjuster or chelating agent. The chelating agent is used for preventing the production of colored compound due to the interaction between metallic ion and tannin in the tannin aqueous solution.
