TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The heat-resistant inorganic oxide contains 0.4-40 wt.% of platinum group element. The heat-resistant inorganic oxide supporting platinum group element has average particle diameter of 0.5-20 mum measured using electron probe microanalyzer. 50 wt.% or more of the platinum group element is platinum. The heat-resistant inorganic oxide which supports platinum group element is activated alumina, cerium oxide and/or zirconium oxide. The heat-resistant inorganic oxide (b) is chosen from cerium oxide, zirconium oxide, activated alumina and cerium-zirconium complex oxide. The weight ratio of activated alumina and cerium oxide contained in catalyst component is 100:15-100:60 and the weight ratio of cerium oxide and zirconium oxide is 100:2-100:60.Preferred Gas: The mixed gas contains water vapor. EXAMPLE - Activated alumina having specific surface area of 155 m2/g was impregnated with a mixed solution containing nitric acid aqueous solution containing rhodium and dinitro diamine platinum. The activated alumina was dried at 150 degrees C for 15 hours, moisture content was removed and baked at 400 degrees C for 2 hours and activated alumina supporting rhodium (0.27 wt.%) and platinum (0.53 wt.%) was produced. Cerium carbonate fine particle was baked at 400 degrees C for 2 hours and cerium oxide powder was obtained by grinding. The cerium oxide powder was added with zirconyl oxynitrate aqueous solution and uniformly mixed so that the weight ratio of cerium oxide to zirconium oxide was 100:30. The obtained mixed slurry was dried at 120 degrees C, moisture content was removed and baked at 500 degrees C for 1 hour to obtain cerium-zirconium complex oxide. The platinum group element supported on activated alumina (111.3), cerium zirconium complex oxide (36.0), pure water and acetic acid were mixed and supplied to ball mill and aqueous slurry was prepared. Honeycomb support made of cordierite was immersed in the slurry and the support was removed from the slurry. Excess slurry was removed from the support and dried at 150 degrees C and baked at 500 degrees C for 1 hour and catalyst component containing support was prepared. The catalyst-containing support was further immersed in the slurry and the process was repeated until catalyst component (9.8) was supported on the support. The weight ratio of activated alumina:cerium oxide:zirconium oxide was 100:25:7.5.    Mixed gas containing oxygen-containing gas (air) and town gas (87.3% methane having sulfur content of 5 ppm) was supplied as reactive gas into a reactor filled with the catalyst. Temperature of the gas was maintained at 350 degrees C and the catalyst layer was over 800 degrees C. The gas produced during the reaction was analyzed by gas chromatography. The conversion ratio of town gas was 79% and the selectivity of hydrogen and carbon monoxide were 89% and 81% respectively.