The proper processing technology of hydrocarbon refrigerant isobutane (R600a) is required to prepare for recycling of the refrigerator. Isobutane extracted from the refrigerator compressor is diluted with air below the flammable range, is oxidized to CO_2 and H_2O by using a palladium catalyst. This paper describes the prototype isobutane oxidation system and its oxidation characteristics. In order to maintain the catalytic conversion efficiency highly, it is required to keep the catalyst inlet gas temperature more than 623K. Exhaust gas recirculation is effective for preheating of gas temperature.