Diesel engine has been utilized in transportation, such as in heavy machinery for agricultural usage, automotive vehicle and ocean ships, because of its high thermal efficiency. However, due to the characteristics of the combustion mechanism, many NOx and SOx are emitted. For the expansion of their uses, these environmental pollutants should be purified. We aimed to establish SOx purification technology by using MnO2 filter. In our previous study, we found that MnO2 can absorb not only SO2 but also NO2 simultaneously. In this study, to improve absorption performance of SO2 and NO2, we added ozone in exhaust gas. Therefore, we investigated the effect of ozone on the desulfurization and denitration performances experimentally. Results showed that maintaining the absorption rate of 90% or more in SO2 and NO2 absorption was possible by adding ozone. The amount of NO2 absorption significantly increased by adding ozone. However, the utilization rate of MnO2 exceeded the theoretical absorption amount. This result suggested that SO2/NO2 purification may have not only a simple absorption reaction but also a purification reaction similar to reduction denitration.