The present invention relates to a method for preparing a catalyst comprising a ruthenium-containing catalyst layer highly dispersed with a uniform thickness on a surface of a substrate having a structure, which comprises first aging a mixed solution of a ruthenium precursor-containing solution and a precipitating agent to form a ruthenium-containing precipitate seeds, secondarily aging the first aged mixed solution to grow the seeds thereby forming ruthenium-containing precipitate particles, and then contacting the particles with a substrate to deposit the particles on the surface of the substrate. Since the catalyst has a structure in which the round shaped ruthenium-containing precipitate particles are piled to form the ruthenium-containing catalyst layer, it has a large specific surface area. Thus, the catalyst may exhibit excellent catalytic performance in various reactions for producing hydrogen using a ruthenium catalyst.