An apparatus and method are provided for manufacturing an electrode of hydrous ruthenium oxide thin film, consisting of an injector for spraying a precursor solution, a substrate for depositing the precursor solution, a base for supporting the substrate and a halogen lamp for heating the substrate, a DC power supply connected to the injector and base, a space adjuster for adjusting the spraying space between the injector and the base, and temperature controller for controlling the temperature of the base. Because of the strong electric field, the sprayed ruthenium precursor solution atomizes the nano-sized very fine particles. Therefore, the atomized particles are deposited on the substrate to form a very fine porous thin film under the influence of electrically charged molecular actions without the influence of gravitation force. The ruthenium oxide electrode formed the fine porous thin film has excellent property of super capacitor, composite electrode of ruthenium oxide and activated carbon.