An organic electrolytic solution for a lithium-sulfur battery that can improve discharge capacity and cycle life of the battery, and a lithium-sulfur battery using the organic electrolytic solution are provided. The electrolytic solution includes a lithium salt, an organic solvent, and further a phosphine sulfide-based compound represented by formula (I) below: wherein R1, R2 and R3 are the same or different from each other, and each represents one selected from the group consisting of a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C1-C30 alkoxy group and a substituted or unsubstituted C8-C30 aralkenyl group. The electrolytic solution including the phosphine sulfide-based compound represented by Formula (I) can suppress production of lithium sulfides so that a reduction in battery capacity can be prevented.