Remarkable enhancement in catalytic activity of a non-platinum catalyst for oxygen reduction in alkaline solutions has been achieved by an oxidative pretreatment of a high-area carbon support before dispersion of catalyst precursor (cobalt hexacyanoferrate), followed by pyrolyzing the precursor under an inert atmosphere. The polarization potential for oxygen reduction at substantial current densities at room temperature under air was higher than a potential corresponding to a limit of relative predominance for O-2/HO2- couple.