A separation membrane for a lithium secondary battery, the separation membrane comprising: a substrate; a first coating layer containing a first organic binder which is able to be bonded to a gel polymer electrolyte through an epoxy ring-opening reaction; and a second coating layer containing a second organic binder, wherein the first organic binder is polyvinylidene fluoride in which an epoxy group is substituted or copolymer of polyvinylidene fluoride and hexafluoropropylene in which an epoxy group is substituted, and the gel polymer electrolyte is formed by polymerizing an oligomer including at least one compound selected from the group consisting of compounds represented by Formulae 1 and 2 below, wherein the separation membrane has a structure in which the first coating layer is formed on the substrate and the second coating layer is formed on the first coating layer, or the second coating layer is formed on the substrate and the first coating layer is formed on the second coating layer: in Formula 1, n1 is an integer of 2 to 10,000; and in Formula 2, R 6 to R 11 are a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R 12 to R 16 are each independently at least one selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, - NR 17 R 18, and -R 19 NR 20 R 21, wherein R 19 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and R 17, R 18, R 20, and R 21 are each independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and -R 22 NH 2, wherein R 22 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and n2 is an integer of 1 to 10,000. a substrate; a first coating layer containing a first organic binder which is able to be bonded to a gel polymer electrolyte through an epoxy ring-opening reaction; and a second coating layer containing a second organic binder, wherein the first organic binder is polyvinylidene fluoride in which an epoxy group is substituted or copolymer of polyvinylidene fluoride and hexafluoropropylene in which an epoxy group is substituted, and the gel polymer electrolyte is formed by polymerizing an oligomer including at least one compound selected from the group consisting of compounds represented by Formulae 1 and 2 below, wherein the separation membrane has a structure in which the first coating layer is formed on the substrate and the second coating layer is formed on the first coating layer, or the second coating layer is formed on the substrate and the first coating layer is formed on the second coating layer: in Formula 1, n1 is an integer of 2 to 10,000; and in Formula 2, R 6 to R 11 are a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R 12 to R 16 are each independently at least one selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, - NR 17 R 18, and -R 19 NR 20 R 21, wherein R 19 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and R 17, R 18, R 20, and R 21 are each independently hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and -R 22 NH 2, wherein R 22 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and n2 is an integer of 1 to 10,000.