PURPOSE: To maintain a sufficient yield of ozone and to prevent an accident in a generating apparatus for ozone by measuring the temp. of an adsorbent in an adsorption tower of the apparatus to detect a rise in the dew point of air and by giving a warning.

CONSTITUTION: Starting material air to be fed to an ozonizer is passed through one of 2 adsorption towers. While moisture is being adsorbed in one of the towers, an adsorbent is regenerated in the other. Temp. switches 6h, 6i are attached to the adsorption towers 6a, 6b, respectively tomeasure the temp. of the adsorbent at the end of a heating stage, and when the temp. is reduced to below the set temp. value, a warning signal is sent to the outside. At this time, the relation between the temp. of the adsorbent at the end of the heating stage and the dew point of dry air in an adsorption stage is established beforehand, and it is used as the warning setting value. A control circuit which stops the generation of ozone and the operation of the ozonizer as soon as it receives the warning signal is installed. Thus, a simple and inexpensive generating apparatus for ozone can be constructed without installing a dew indicator.