NOVELTY - A polyester film has polyester layer containing polyester component comprising polyester and 0.1-10 %mass terminal blocking agent with respect to polyester, and 0.1-10 %mass microparticles (31) with respect to polyester in polyester component. The polyester is 1,4-cyclohexane dimethanol-type polyester in which a diol component comprises 0.1-20 mol% or 80-100 mol% of structures derived from 1,4-cyclohexane dimethanol. The microparticles are surrounded by voids (32).    USE - Polyester film is used for backsheet of solar cell module (all claimed).    ADVANTAGE - The polyester film has excellent hydrolysis resistance, reflectance and thermally-conductive efficiency. The solar cell module obtained using polyester film has excellent wet heat durability and electric power generation efficiency.    DETAILED DESCRIPTION - A polyester film has polyester layer containing polyester component comprising polyester and 0.1-10 %mass terminal blocking agent with respect to polyester, and 0.1-10 %mass microparticles with respect to polyester in polyester component. The polyester is 1,4-cyclohexane dimethanol-type polyester in which a diol component comprises 0.1-20 mol% or 80-100 mol% of structures derived from 1,4-cyclohexane dimethanol. The microparticles are surrounded by voids. The average value of ratio (Lb/Lp) line segment (Lb) except the portion which overlaps with the orthogonal projection to the film cross section of the microparticles among the long sides of the orthogonal projection to the film cross section of the void which exists in the circumference of one microparticle, and long side (Lp) of the orthogonal projection of the one microparticle onto the film cross section, is 0.5-2.0. An INDEPENDENT CLAIM is included for manufacture of polyester film, which involves melt-kneading polyester and microparticles by providing 0.1-5% fluctuation to a screw speed, extruding melt substance, molding to film and extending the obtained film.    DESCRIPTION OF DRAWING(S) - The drawing shows cross-sectional view of polyester film.    Microparticles (31)    Void (32)    Long side of orthogonal projection to the film cross section of whole void which exists in one microparticle and its circumference (L0)    Line segment except the portion which overlaps with the orthogonal projection to the film cross section of the microparticles among the long sides of the orthogonal projection to the film cross section of the void which exists in the circumference of one microparticle (Lb)    Long side of the orthogonal projection of one microparticle onto the film cross section (Lp)