NOVELTY - A gas-barrier film (100) comprises anchor-coat layer (3) having urethane bond, inorganic vapor deposition layer (4) which consists of inorganic compounds and composite film layer (5) which are successively laminated on single surface of polyester base material (1), and easily bonding layer (2) which consists of water-based polyester resin between polyester base material and anchor-coat layer. The composite film layer applies liquid containing 1st type of compound which is hydroxyl-containing high molecular compound, and 2nd type of compounds which are metal alkoxide or its hydrolyzate.    USE - A gas-barrier film used for back surface and front surface protection sheets for solar cell modules (all claimed).    ADVANTAGE - Heat resistance, weather resistance, hydrolysis resistance, damp-proofness and lightness are excellent. Penetration of water vapor is prevented. Protection sheet is inexpensive.    DETAILED DESCRIPTION - A gas-barrier film (100) comprises anchor-coat layer (3) having urethane bond, inorganic vapor deposition layer (4) which consists of inorganic compounds and composite film layer (5) which are successively laminated on single surface of polyester base material (1), and easily bonding layer (2) which consists of water-based polyester resin between polyester base material and anchor-coat layer. The composite film layer applies liquid containing 1st type of compound which is hydroxyl-containing high molecular compound, 2nd type of compounds which are metal alkoxide or its hydrolyzate and 3rd type of compounds which are silane coupling agent or its hydrolyzate. The terminal carboxyl group concentration in polyester of polyester base material is less than or equal to 25 g equivalent/106 g. INDEPENDENT CLAIMS are included for:    (1) back surface protection sheet for solar cell modules comprising colored film which is bonded on single surface of gas-barrier film, and weather-resistance film which is bonded to another surface; and    (2) front protection sheet for solar cell modules comprising UV-blocking film and transparent weather-resistance film which are bonded on single surface of gas-barrier film.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional conceptual view of the gas barrier film.    Polyester base material (1)    Easily bonding layer (2)    Anchor-coat layer (3)    Vapor deposition layer (4)    Composite film layer (5)    Gas-barrier film (100)