Patented is a polyester release film with a maximum height of projection (Rmax) of one surface of not more than 500 nm. The film has a number of projections with a height of not less than 350 nm and not more than 200 per mm2. It has a thickness variation defined by the following equation using the maximum, minimum and mean values of film thickness in the machine and transverse directions of the polyester film of not more than 5%: thickness variation (%) = (maximum thickness - minimum thickness) x 100/average thickness.