Polyethylene-terephthalate (PET) films coated with photocatalytic TiO₂ and silicone as a binder were fabricated and attached to a window pane. A white substance was observed on the surface after exposure for several months in an area with air pollution. The white substance was analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy, ion chromatograph and capillary electrophoresis, and was identified as CaSO₄. Although the oxidizing properties of the films were affected by the particle size and the amount of TiO₂ in the photocatalytic layer, the hydrophilicizing properties of the films were hardly changed by them. In this study, we found that it was possible to decrease the oxidizing properties of photocatalytic PET films while maintaining the hydrophilicizing properties constant by using small TiO₂ particles and controlling the ratio of TiO₂/binder.