There exist two types of photo-induced effects on TiO₂ surface. One is the conventional photocatalytic reaction and the other is photo-induced highly hydrophilic conversion, proceeding on the TiO₂ surface irradiated with UV light. Various materials coated with TiO₂ transparent films can show self-cleaning, anti-fogging, and cooling effects with small amount of water. Their industrial applications are also introduced. Moreover, the mechanism for the highly hydrophilic conversion is suggested, considering the recent experimental results. That is, not the conventional photocatalytic decomposition of the strains on the TiO₂ surface but the increase in the amount of hydroxyl groups on its surface irradiated with UV light is responsible for the hydrophilic conversion.