Hydroxyapatite coated on TiO2 for use as a photocatalyst for water purification was synthesized by using the superhydrophilicity of TiO 2. The hydroxyapatite formed on TiO2 under UV irradiation with high crystallization in 1 h. The isoelectric point of the hydroxyapatite-coated TiO2 was shifted to acidic pH, and the aggregates formed in aqueous solution at pH 7 were smaller than those of anatase TiO2. Consequently, in water purification tests, the proposed photocatalyst effectively decomposed dimethyl sulfoxide and Methylene Blue in water. © 2013 The Chemical Society of Japan.