A separator for an electrochemical device, including a porous substrate and a porous coating layer on at least one side of the porous substrate. The porous coating layer includes a binder resin, inorganic particles, and an ionic dispersant. The inorganic particles include plate-shaped particles a having a Mohs hardness of 3 or less and a density of 3 g/cm3 or less, in which the plate-shaped particles a contain kaolin. The separator can be implemented to be thinner and lighter than conventional counterparts, has improved heat shrinkage characteristics, and is not easily damaged under pressure.