NOVELTY - A polyester resin having biphenyl group-containing structural units (I) and (II) is stretched at ratio of 1.15-1.3 along vertical and horizontal directions at temperature of (Tg-20 degrees C) to (Tg+35 degrees C) (Tg is glass transition temperature of polyester resin). Both ends of stretched resin are held by fixed space along horizontal direction at temperature of (Tg-30 degrees C) to (Tg-10 degrees C), and heat-treated. The edge portion of resulting resin is held at temperature of (Tg-50 degrees C) to (Tg-30 degrees C) along horizontal direction and heat-treated to manufacture polyester resin film.    USE - Manufacture of polyester resin film for solar cell (claimed), touch panel and image display apparatus including liquid crystal display, organic electroluminescent display, inorganic electroluminescent display, fluorescent display tube, light emitting diode and field emission display.    ADVANTAGE - The polyester resin film has excellent heat resistance.    DETAILED DESCRIPTION - A polyester resin having biphenyl group-containing structural units of formulae (I) and (II) is stretched at ratio of 1.15-1.3 along vertical and horizontal directions at temperature of (Tg-20 degrees C) to (Tg+35 degrees C) (Tg is glass transition temperature of polyester resin). Both ends of stretched resin are held by fixed space along horizontal direction at temperature of (Tg-30 degrees C) to (Tg-10 degrees C), and heat-treated. The edge portion of resulting resin is held at temperature of (Tg-50 degrees C) to (Tg-30 degrees C) along horizontal direction and heat-treated to manufacture polyester resin film.    R11-R14,R21-R26=H or substituent, and at least one of R21-R26 is substituent;and    R15-R18=substituent.    An INDEPENDENT CLAIM is included for polyester resin film.    DESCRIPTION OF DRAWING(S) - The drawing shows the block diagram of production line of polyester resin film. (Drawing includes non-English language text)    Production line (10)    Melt extruder (20)    Die (22)    Casting drum (24)    Heat-processing apparatus (90)