Disclosed is a separator including a separator substrate and an inorganic coating layer disposed on at least one surface of the substrate, wherein a concave pattern portion having a concave pattern is applied merely at the outer circumferential end of the separator substrate. The separator may show excellent resistance characteristics, while ensuring high binding force between the separator substate and the inorganic coating layer by virtue of such a structural feature. In addition, in the electrochemical device including the separator, the concave pattern portion at the outer circumferential end of the separator is disposed in such a manner that it may be overlapped with the tab portion of an electrode, when the separator is applied to an electrode assembly. In this manner, it is possible to prevent lithium plating.