A method for manufacturing separators includes (S1) treating at least one of the laminating surfaces of two porous substrates by corona discharge and laminating the porous substrates, (S2) preparing a slurry containing inorganic particles dispersed therein and a solution of a binder polymer in a solvent, and coating the slurry on both surfaces of the laminate of the porous substrates, and (S3) delaminating the coated laminate of the porous substrates. According to the method, two separators can be simultaneously manufactured with enhanced productivity. In addition, corona discharge can reduce damage to the surfaces of the porous substrates during lamination while maintaining the porosities of the porous substrates. Therefore, excellent performance of electrochemical devices using the separators can be ensured.