An ozone generator in which a discharge region may be enlarged without damaging ozone generating performance. In the ozonizer, an alternating current is applied between a first electrode and a second electrode, and a discharge is produced in a gap into which oxygen is injected. In the first electrode, an ozone gas passage for retrieving ozone gas generated in the discharge region is located between an electrode surface facing the discharge region and a side. The ozone gas passages are dispersed in the first electrode. The ozone gas passages collect ozone generated at discharge region locations inside the first electrode.