A separator includes a substrate and a coating layer on at least one surface of the substrate, wherein the coating layer includes first organic particles and second organic particles, an average particle diameter of the first organic particles is larger than an average particle diameter of the second organic particles, the first organic particles protrude a height of about 0.1 µm to about 0.5 µm from a dented portion of a surface of the coating layer and are distributed on the surface of the coating layer in an area ratio from 5% or greater to less than 30% with respect to a total surface area of the coating layer. Using the separator, a lithium battery may have improved adhesion to electrodes, improved insulation characteristics and air permeability, and improved lifespan characteristics.