a method for the production of biaxially stretched polyester film . the method comprises the steps of : adding cubic calcium carbonate particles of calcite structure satisfying the following conditions at any stage of polyester preparation , so as to prepare polyester resin : d . sub . 25 / d . sub . 75 & lt ; 2 . 00 0 . 7 ≦ d . sub . 50 ≦ 1 . 50 a : b : c = 1 :: wherein d 25 , d 50 and d 75 are the diameters of particles when the accumulated weights of the particles are on the order of 25 , 50 and 75 % of the total weight of the particles , respectively , and a , b , c are width , length and height of the cubic calcium carbonate particles and the shortest one among a , b and c is set a = 1 ; and applying melt - extrusion to the polyester resin . the biaxially stretched copolyester film provided is superior in travelling capacity as well as abrasion resistance and scratch resistance , so that it is useful for magnetic recording media .