To provide a heat-resistant oxide which is excellent in heat resistance and durability at high temperature and has high activity, a heat-resistant oxide which has an oxide crystal structure and in which a rate of a solid solution of a noble metal in the oxide crystal structure is 50% or more is obtained by heat-treating (secondarily baking) a precursor composition comprising zirconia, at least one coordinative element selected from the group consisting of rare earth elements, alkaline earth elements, aluminum and silicon, and at least one noble metal selected from the group consisting of platinum, rhodium and palladium at 650.degree. C. or higher.