The present disclosure relates to a method of manufacturing catalyst slurry for fuel cells capable of greatly improving efficiency in use of catalyst metal and a method of manufacturing an electrode for fuel cells using the catalyst slurry manufactured using the method. Specifically, the method of manufacturing catalyst slurry for fuel cells includes preparing a catalyst including a porous carrier and catalyst metal, introducing the catalyst, a solvent, and an ionomer into a chamber, and infiltrating the ionomer into pores of the carrier.