The present invention relates to a cathode containing a solid superacid to improve the electrochemical properties and lifetime properties of the cathode using sulfur as an active material, and to a lithium-sulfur secondary battery including the cathode. According to an embodiment, a cathode for a lithium-sulfur secondary battery contains sulfur and a solid superacid. Since the solid superacid in the cathode does not affect the electrochemical properties of the cathode containing sulfur, it is possible to utilize sulfur itself as the cathode active material without technical processing. As a result, it is possible to minimize a reduction in the energy density of the lithium-sulfur secondary battery. In addition, the solid superacid in the cathode can improve the long-term lifetime properties of the lithium-sulfur secondary battery by controlling the polysulfide which is an intermediate product of the charging and discharging reactions of lithium and sulfur.