Disclosed is a method for manufacturing a separator. The method includes (S1) preparing a slurry containing inorganic particles dispersed therein and a solution of a binder polymer in a solvent, and coating the slurry on at least one surface of a porous substrate to form a first porous coating layer, and (S2) electroprocessing a polymer solution on the outer surface of the first porous coating layer to form a second porous coating layer. The first porous coating layer formed on at least one surface of the porous substrate is composed of a highly thermally stable inorganic material to suppress short-circuiting between an anode and a cathode even when an electrochemical device is overheated. The second porous coating layer formed by electroprocessing improves the bindability of the separator to other base materials of the electrodes.