Titanium alloy Ti-6Al-4V was galvanostatically anodized in an aqueous acetic acid electrolyte followed by annealing to form anatase-structured TiO2. The formed pale yellowish oxide contained Al3+, V5+, and V4+ in the topmost surface of the anodized oxide. The anodized TiO2 photocatalytically decomposed acetaldehyde under visible light illumination (>400 nm).