To prevent a decrease in the ozone concentration in ozone water due to the reduction of the amount of generated ozone gas by preventing water from flowing into an ozone generator.

An ozone generating apparatus 1 includes a raw liquid transfer part 10 for continuously and quantitatively transferring a raw liquid, an ozone gas generating part 20 for generating ozone-containing ozone gas, a gas-liquid mixing part 30 for mixing the ozone gas into the raw liquid to generate gas-liquid mixed water, and a gas-liquid separation part 40 for separating the gas-liquid mixed water into waste gas and ozone water to store them. In the ozone gas generating part 20, a water separator 24 is provided between an ozone generator 23 and a mixer 32, and when waste water flowing backward from the mixer 32 is collected in the water separator 24 by a predetermined amount, a drain solenoid valve 25 is opened to discharge the waste water.