NOVELTY - A polyethylene terephthalate resin film has refractive index difference ( Delta nab) at 45 degrees and 90 degrees of 0.015-0.06. The ratio (TS/TE) of breaking elongation (TE) and breaking strength (TS) of winding direction of film which forms a 45 degrees angle, 135 degrees angle and 90 degrees angle are 0.6-2.6 MPa/%. HS150, which is the thermal contraction rate of film at winding-up direction when heated for 30 minutes at 150 degrees C, is calculated for five samples cut out from the center part in the width direction of each film divided into 5 at greater than or equal to 70 cm, the difference of the maximum and minimum values of HS150 less than or equal to 0.1 %.    USE - Bi-axial stretching polyethylene terephthalate resin film roll for base film for prism lens sheets, back lights, anti-reflection film, crushing prevention film for cathode ray tube, optical film for optics or processing film for solar cell.    ADVANTAGE - The film has excellent post-processing characteristics such as permeability in heat treatment process during post processings such as prism lens processing, hard coat processing and antireflective processing, post processing can be carried out with a very high yield and manufacturing process is inexpensive.    DETAILED DESCRIPTION - A polyethylene terephthalate resin film has refractive index difference ( Delta nab) at 45 degrees and 90 degrees of 0.015-0.06. The ratio (TS/TE) of breaking elongation (TE) and breaking strength (TS) of winding direction of film which forms a 45 degrees angle, 135 degrees angle and 90 degrees angle are 0.6-2.6 MPa/%. HS150, which is the thermal contraction rate of film at winding-up direction when heated for 30 minutes at 150 degrees C, is calculated for five samples cut out from the center part in the width direction of each film divided into 5 at greater than or equal to 70 cm, the difference of the maximum and minimum values of HS150 less than or equal to 0.1 %. HS150 of five samples are -0.25 to 0.25%. The difference of minimum and maximum values of HS180, which is the thermal contraction rate of film winding-up direction when heated for 30 minutes at 180 degrees C degree, is less than or equal to 0.1%. HS180 of five samples are 0.4-1.15%. Thickness coefficient of variation of winding direction of film is less than or equal to 6 %. Thickness of film is 70 to 400 mu m. An INDEPENDENT CLAIM is included for manufacture of polyethylene terephthalate resin film.