NOVELTY - A solar-cell back-surface protection sheet has weather-resistant flame-resistant resin layer (1), plastic film (2), and easily-adhesive layer (3). The weather-resistant flame-resistant resin layer contains phosphorus-based flame retarder (A) chosen from phosphazene compound, phosphinic acid compound and (poly)melamine phosphate, and weather-resistant resin (B) chosen from polyester-based resin, fluorine resin and urethane-type resin. The film thickness (t) of weather-resistant flame-resistant resin layer is 2.5-20% of total thickness of the protection sheet.    USE - Solar-cell back-surface protection sheet used for solar cell module (claimed).    ADVANTAGE - The solar-cell back-surface protection sheet has excellent heat-and-moisture resistance and long-term outdoor weather resistance, and efficiently and economically provides solar cell module with excellent workability.    DETAILED DESCRIPTION - A solar-cell back-surface protection sheet has weather-resistant flame-resistant resin layer having film thickness of t micro m, plastic film, and easily-adhesive layer. The weather-resistant flame-resistant resin layer comprises a surface on one side of the solar cell back surface protection sheet. The easily-adhesive layer comprises the surface on other side of solar cell back surface protection sheet. The weather-resistant flame-resistant resin layer contains phosphorus-based flame retarder (A) chosen from phosphazene compound, phosphinic acid compound, (poly)melamine phosphate and fluorine resin, urethane-type resin, and weather-resistant resin (B) chosen from polyester-based resin. The film thickness (t) of the weather-resistant flame-resistant resin layer is 2.5-20% of the total film thickness of the solar cell back surface protection sheet. The total phosphorus concentration derived from the phosphorus-based flame retarder (A) in the weather-resistant flame-resistant resin layer is 2.1-14.2 wt.%. An INDEPENDENT CLAIM is included for solar cell module.    DESCRIPTION OF DRAWING(S) - The drawing shows sectional view of solar-cell back-surface protection sheet.    Weather-resistant flame-resistant resin layer (1)    Plastic film (2)    Easily-adhesive layer (3)