Abstract: An apparatus and a method are provided for manufacturing an electrode of hydrous ruthenium oxide thin film. The apparatus comprises an injector for introducing a precursor solution and spraying the precursor solution; a substrate having the precursor solution sprayed thereon; a substrate-supporting base for supporting the substrate and including a halogen lamp therein for heating the substrate; a direct current power supply connected to the substrate-supporting base and the injector; a distance adjuster for adjusting the distance between the substrate-supporting base and the injector; and a temperature controller for controlling the substrate-supporting base. Under a strong electric field, the ruthenium precursor solution is sprayed, to yield a porous thin film electrode having very fine particles.