Abstract: The present invention relates to a solid electrolyte consisting essentially of cerium oxide for a fuel cell. In addition, this solid electrolyte is prevented from becoming reduced under the effect of a fuel gas of a fuel cell. The present invention also relates to a method for producing this solid electrolyte and to a high-temperature-type fuel cell utilizing this solid electrolyte. This solid electrolyte for a fuel cell comprises:(a) a specifically-shaped solid electrolyte consisting essentially of cerium oxide; the solid electrolyte having a fluorite-type structure and oxide-ionic conduction; and(b) a perovskite-type oxide having an ABO.sub.3 -type composition, which is a solid electrolyte of proton/oxide-ionic mixed conduction and is bonded as a membrane on a part of the surface of the solid electrolyte consisting essentially of cerium oxide, in which(i) A of the "ABO.sub.3 " represents at least one element selected from the group consisting of alkaline earth metals; and(ii) B of the "ABO.sub.