NOVELTY - A fluororesin film (11) contains ethylene-tetrafluoroethylene copolymer and titanium oxide composite particles. The composite particles are obtained by hydrophobically treating silica-coated titanium oxide particles, by a hydrophobic agent. In the silica-coated particles, the quantity of silica coating layer with respect to 100 parts mass of titanium oxide particles is 1.5-5 parts mass by silica conversion. In the composite particles, the quantity of hydrophobic agent is 0.5-10 parts mass with respect to 100 parts mass of silica-coated particles.    USE - Fluororesin film is used for back sheets of solar cell modules (both claimed).    ADVANTAGE - The fluororesin film has excellent deterioration resistance, heat resistance, and weather resistance, and low transmittance with respect to UV light of wavelength 360 nm or less. Bubble lines are not formed even when a sufficient amount of titanium oxide is contained. The fluororesin film provides back sheets which stably protect the solar cell modules over a long period of time, and the solar cell modules can be used over a long period of time. The back sheet can be used suitably in solar cell modules installed at an optimal angle according to the latitude of installation place.    DETAILED DESCRIPTION - A fluororesin film contains ethylene-tetrafluoroethylene copolymer as main component, and titanium oxide composite particles. The arithmetic mean deviation on the surface of the film contacting atmosphere is 3 mu m or less as measured by JIS B0601. The titanium oxide composite particles are obtained by hydrophobically treating silica-coated titanium oxide particles having a silica coating layer formed on the surface of titanium oxide particles, by a hydrophobic agent. In the silica-coated particles, the quantity of silica coating layer with respect to 100 parts mass of titanium oxide particles is 1.5-5 parts mass by silica conversion. In the silica-coated particles, the difference of Karl-Fischer moisture content (300 degrees C and 100 degrees C) is 0.5% or less. In the composite particles, the quantity of hydrophobic agent is 0.5-10 parts mass with respect to 100 parts mass of silica-coated particles. INDEPENDENT CLAIMS are included for the following:    (1) back sheet (1);    (2) solar cell module; and    (3) usage method of fluororesin film.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the back sheet.    Back sheet (1)    Fluororesin film (11)    Film surface (11a)    Adhesive layer (12)    Water-vapor barrier (13)