Abstract: A method of producing a superconductor of metal oxides having the following composition:(M.sub.1-x Ca.sub.x)(Ba.sub.1-y Sr.sub.y).sub.2 Cu.sub.4 O.sub.8wherein M stands for a rare earth element, x is 0 or a positive number of less than 1 and y is 0 or a positive number of less than 1, is disclosed, which includes hydrdolyzing an organic solvent solution or dispersion containing (a) alkoxide or fine particulate of a hydroxide of the rare earth element M, (b) alkoxides orfine particulate of hydroxides of Ca, Ba and Sr and (c) alkoxide, nitrate or fine particulate of hydroxide of copper in presence of water and nitrate ions. The alkoxides or hydroxides of Ca and Sr are present only when x and y are not zero, respectively. The hydrolyzed product is then dried, shaped and pyrolyzed to obtain the superconductor.