The present invention relates to a method for manufacturing a separator in which the tensile strength is enhanced and melt shrinkage is reduced by controlling elongation step from among the manufacturing steps thereof. Additionally, the present invention relates to a separator having superb winding processability as well as superb thermal stability due to the raised the tensile strength while maintaining a low rate of melt shrinkage. Furthermore, the present invention relates to an electrochemical battery having enhanced stability by utilizing a separator having high tensile strength and a low rate of melt shrinkage.