Abstract: Disclosed is a noble metal-manganese oxide composite catalyst for a positive electrode of an aqueous rechargeable battery that can regenerate a solvent of an aqueous electrolyte. Also disclosed are a method for preparing the composite catalyst, a positive electrode for an aqueous rechargeable battery including the composite catalyst, and an aqueous rechargeable battery including the positive electrode. The composite catalyst can regenerate reaction products, including gases continuously generated from spontaneous corrosion of the electrodes or side reactions, back to water to prevent depletion of the electrolyte. Due to this ability, the composite catalyst improves the life characteristics of the battery and suppresses the occurrence of excessive overpotentials at the electrodes. Therefore, the use of the composite catalyst is effective in preventing the performance of the battery from deteriorating.