A photoresist layer supporting film is (A) formed from a polymer composition comprising (i) 55 to 100% by weight of a copolyester containing ethylene terephthalate units as a main recurring unit and having a melting point of 210 to 250.degree. C. and (ii) 0 to 45% by weight of polybutylene terephthalate or a copolyester containing butylene terephthalate units as a main recurring unit and having a melting point of not lower than 180.degree. C. and (B) has a plane orientation coefficient of 0.08 to 0.16. Since this supporting film is excellent in substrate shape follow-up properties and resolution, it is suitable for the preparation of a photoresist film laminate by laminating a protective film and a photoresist layer on the surface thereof.