The reduction rates of manganese oxide by carbon and SiC was examined by heating MnO2-carbon and MnO2-SiC mixtures in a 7-kW industrial microwave oven. The results show that the rate of the reduction increased with the amount of carbon in MnO2-carbon mixture and with SiC in MnO2-SiC mixture. The rate of the MnO2 reduction by carbon was proportional to the reaction time, and that by SiC was proportional to 2/3 power of the reaction time. The reduction was found to be controlled by chemical reaction. The reaction rate constant of the reduction of MnO2 kC increased with increasing the amount of carbon in the mixtures but kSiC decreased with increasing the amount of SiC in the mixtures.