NOVELTY - A back surface protection sheet (1) has a protective layer (11), a primary layer (12), a polyester-type resin layer (13) and a base material laminated in order. The primer layer consists of polyurethane resin obtained by crosslink-curing urethane-type prepolymer containing urethane prepolymer (A) and urethane prepolymer (B) using isocyanate-type crosslinking agent. The prepolymer (A) is obtained from urethane prepolymer obtained from caprolactone-modified polyester diol and diisocyanate. The urethane prepolymer (B) is obtained from diol component and diisocyanate.    USE - Back surface protection sheet is used for solar cell module (claimed).    ADVANTAGE - The back surface protection sheet has excellent adhesiveness, heat resistance, flaw resistance, weather resistance and durability.    DETAILED DESCRIPTION - A back surface protection sheet has a protective layer, a primary layer, a polyester-type resin layer and a base material laminated in order from back surface side of solar cell module. The base material is obtained using thermoplastic resin. The surface protective layer is obtained by crosslink-curing ionizing radiation hardenable resin composition by ionizing radiation irradiation. The primer layer consists of polyurethane resin obtained by crosslink-curing urethane-type prepolymer containing urethane prepolymer (A) and urethane prepolymer (B) using isocyanate-type crosslinking agent. The prepolymer (A) is obtained from urethane prepolymer obtained from caprolactone-modified polyester diol and diisocyanate. The urethane prepolymer (B) is obtained from diol component chosen from caprolactone-modified polyester diol, polycarbonate diol, acryl diol and polyether diol, and diisocyanate. An INDEPENDENT CLAIM is included for solar cell module.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional view of back surface protection sheet.    Back surface protection sheet (1)    Protective layer (11)    Primer layer (12)    Polyester-type resin layer (13)    Adhesive bond layer (15)