A system including: an ozone generating device including discharge electrodes forming a discharge space; a gas supplying device; a power source device that supplies power to the discharge electrodes; a temperature adjustment device that adjusts temperature of the discharge electrodes; a control unit that controls the ozone generating device; and a detection unit that detects an ozone generation parameter in the ozone generating device. The control unit increases temperature of the discharge electrodes up to a vaporizing temperature of dinitrogen pentoxide by controlling the temperature adjustment device and the gas supplying device or the temperature adjustment device and the power source device, based on the output ozone generation parameter, to thereby switch operation from a normal operation mode to a cleaning operation mode in which surfaces of the discharge electrodes and the discharge space are cleaned up while continuing generation of ozone in the discharge space.