High concentration ozone formation due to the micro gap silent discharge by using cylinder ozone generator which has a glass lining ground electrode and direct cooling type high voltage electrode is discussed. The cooling efficiency of the electrode is high and effective to prevent heat decomposition of ozone. Micro gap ozone generating tube of an discharge gap length of 0.15mm was produced by improvement of the manufacture technology. We confirmed that the discharge gap length is maintained 0.15 mm by measuring a size of electrodes and discharge power versus peak voltage. Discharge maintain voltage is proportional to gas pressure product discharge gap length. Ozone concentration obtained using the micro gap electrode is about 300g/Nm³ at the power density W/S (discharge power/discharge area) of 0.3 watt/cm². This is the same level as the characteristic of the parallel plane electrode with ceramic.