Separator for Secondary Battery and Electrochemical Device Using the Same

Provided are a separator for a secondary battery and an electrochemical device using the same. More particularly, a composite separator which has a lower Gurley permeability after curing than that before curing when forming a heat-resistant coating layer having low resistance, does not have a Gurley permeability which is greatly increased as compared with the Gurley permeability of a porous substrate itself before forming a coating layer to have an overall low Gurley permeability, and has a high surface hardness to have penetration stability, is provided.