Some sintered oxides based on were found to exhibit appreciable proton conduction under hydrogen‐containing atmosphere at high temperature. The verification of proton conduction was made by studying the EMF of various gas cells using the specimen ceramics as the solid electrolyte. The protonic conductivity in the doped was higher than that in the proton conductor found previously by us. These materials could be applied to the solid electrolyte for a hydrogen fuel cell, a hydrogen pump, and a steam electrolyzer to produce hydrogen.