NOVELTY - The device comprises a reactor connected to a center tube according to a progressive direction, a ferric solution tube (12) installed through the center tube, a lithium solution tube (14) connected to the center tube, supercritical water tubes connected to the center tube according to the progressive direction, a main mixer (20) in which the supercritical water is mixed, and a cooling apparatus (15) that prevents the heat generated in the supercritical water flowed in the main mixer and the center tube. The ferric solution tube is extended to an entrance of the main mixer.    USE - The device is useful for manufacturing a lithium transition metal phosphate cathode active material (claimed), which is useful in a lithium secondary battery for hybrid electric vehicle.    ADVANTAGE - The device allows efficient manufacture of the cathode active material with high safety thus increasing the energy density, stability and self-discharge rate of the battery.    DETAILED DESCRIPTION - The device comprises a reactor connected to a center tube according to a progressive direction, a ferric solution tube (12) installed through the center tube, a lithium solution tube (14) connected to the center tube, supercritical water tubes connected to the center tube according to the progressive direction, a main mixer (20) in which the supercritical water is mixed, and a cooling apparatus (15) that prevents the heat generated in the supercritical water flowed in the main mixer and the center tube. The ferric solution tube is extended to an entrance of the main mixer. The center tube is connected to both sides of the lithium solution tube. The supercritical water tube includes a first supercritical water tube (22) inclinedly connected to an upstream side of the center tube, and a second supercritical water tube inclinedly connected to a downstream side of the center tube. The supercritical water tube is inclinedly connected to an extension direction of the center tube and lithium solution tube. The lithium solution tube and supercritical water tube are connected to each other so that the center tube forms an acute angle. The device further comprises a filter for filtering powder of the cathode active material generated in the reactor, and a heat exchanger. An INDEPENDENT CLAIM is included for a mixing apparatus.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a device for manufacturing a cathode active material.    Ferric solution tube (12)    Lithium solution tube (14)    Cooling apparatus (15)    Main mixer (20)    First supercritical water tube. (22)