TiO2 photocatalysts decompose hazardous chemical substances into CO2 and H2O under light irradiation. We formed the TiO2 thin films on the quartz glass plates by RF magnetron sputtering method without heating. After 90-second UV irradiation, the thin films decompose colon bacillus down to 0.1%. Moreover, they absorbed visible light at over 600 nm. We tried to pile up these semiconductor films, whose energy gaps are narrower than 3.2eV. TiO2 thin films absorbed visible light more and caused more efficient photocatalytic reaction. Antibacterial catheters, contact lenses, plastic containers, etc.,were prepared by the RF magnetron sputtering without heating.