A lithium-sulfur battery includes a positive electrode having at least one positive active material selected from the group consisting of an elemental sulfur, Li2Sn (n≧1), Li2Sn (n≧1) dissolved in catholytes, an organosulfur compound, and a carbon-sulfur polymer ((C2Sx)n: x=2.5˜50, n≧2), an electrolyte having salts of an organic cation, and a negative electrode having a negative active material selected from the group consisting of a material capable of reversibly intercalating/deintercalating lithium ions, a material capable of reversibly forming a lithium-containing compound by a reaction with lithium ions, a lithium metal, and a lithium alloy.