The present invention relates to a separator for a secondary battery and a lithium secondary battery including the separator, the separator including: a porous substrate and a heat-resistant layer disposed on at least one surface of the porous substrate, wherein the heat-resistant layer includes an acrylic heat-resistant binder, an adhering binder, and a filler, the acrylic heat-resistant binder including a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing structural unit, and a sulfonate group-containing structural unit, the adhering binder includes a structural unit including a structural unit including hydroxyl group, a structural unit including an acetate group, and a structural unit including an alkali metal.