The Dielectric Barrier Discharge (DBD) is composed of many Filamentary Discharges (FDs), and it can be applied to ozone generation, gaseous pollution control, etc. In our laboratory, we investigated efficient cleaning methods of diesel exhaust gas by DBD. From the results of numerical simulation of chemical reactions, a homogeneous DBD was expected to improve the efficiency of pollution control and also the ozone yield. Recently, we found that a DBD device using alumina as barrier material can generate an Atmospheric Pressure Townsend Discharge (APTD) in air. In this research, we setup two ozonizers with different discharge modes of FD and APTD, and compared the ozone yield. The experimental results showed that the ozone yield was higher by the FD mode than by the APTD mode in lower Specific Input Energy (SIE) region. However in the region that the SIE is larger than 420J/L, the APTD mode showed higher ozone yield than FD mode.