A separator includes a porous substrate having a plurality of pores; and a porous coating layer formed on at least one surface of the porous substrate and made of a mixture of a plurality of inorganic particles and a binder polymer, wherein the binder polymer includes a first polyvinylidene fluoride based copolymer having solubility of 25 weight % or more with respect to acetone at 35° C.; a second polyvinylidene fluoride-based copolymer having solubility of 10 weight % or less with respect to acetone at 35° C.; and a polymer having a cyano group. This separator decelerates deterioration of life span of an electrochemical device, and prevents disintercalation of inorganic particles in the porous coating layer, thereby improving safety of the electrochemical device.