The applicability of the highly porous ruthenium oxide electrode designed by dissolution of lanthanum from a RuO 2 -La 2 O 3 /Ti electrode to the electrocatalyst support of a platinum particle electrode was examined. Both the broadness of the X-ray diffraction peaks and the large exposed surface area of the loaded platinum particles showed that the embedded platinum particles were highly dispersed on the porous ruthenium oxide surface. The dependence of the platinum loading on the electrocatalytic activity of the electrode for hydrogen evolution also showed that platinum can be loaded more than 10 mol% retaining the high dispersion of platinum. Thus, the highly porous ruthenium oxide electrode prepared from RuO 2 -La 2 O 3 /Ti electrode was clarified to serve as a novel support for the noble metal particle electrodes.