An ozone generator includes a housing having an internal cavity and a plurality of electrode pairs located in the internal cavity. The electrode pairs each contain two electrodes arranged at a distance of a predetermined gap length, and a discharge space is formed between the two electrodes, whereby ozone is produced when a source gas flows at least between the two electrodes and a discharge is generated between the two electrodes. The ozone generator has a non-discharge portion in an arbitrary cross-section having a normal direction parallel to a main flow direction of the source gas in the internal cavity.