PROBLEM TO BE SOLVED: To form a thick titanium oxide layer on the surface of a material to be coated to increase a photocatalysis by titanium oxide.SOLUTION: A method for coating titanium oxide includes a coating film formation process of coating amorphous titanium oxide on the surface of a material to be coated in a film state, and a UV-ray irradiation process of irradiating the coated amorphous titanium oxide with the UV ray to crystallize. A titanium oxide layer is formed on the surface of the material by the UV-ray irradiation after repeating the coating film formation process several times. Further, a thick titanium oxide layer is formed on the surface of the material by repeating the above film formation and irradiation processes alternately several times. Besides, the titanium oxide layer is formed on the surface of a filter using the above method.SELECTED DRAWING: Figure 1
