A method of manufacturing a cathode active material, according to the inventive concept includes: disposing a lithium transition metal oxide and a washing liquid into a reaction chamber; contacting the lithium transition metal oxide with the washing liquid to wash the lithium transition metal oxide and form a washed lithium transition metal oxide; disposing a layered double hydroxide into the reaction chamber to form a coating of the layered double hydroxide on a surface of the washed lithium transition metal oxide to provide a coated lithium transition metal oxide; and heat treating the coated lithium transition metal oxide to form a cathode active material, wherein the cathode active material comprises a layered double oxide coated lithium transition metal oxide, and wherein the contacting the lithium transition metal oxide with the washing liquid and the forming of the coated lithium transition metal oxide are consecutively performed in a single space.