To provide a circulation drying device operating method for canceling the spray of an dried object into a dryer without a great change in the temperature of gas in the outlet of the dryer and in the pressure of gas in a device.

The operating method is provided for a circulation drying device 10 which has a means for automatically adjusting the spray amount of latex or water so that the temperature of gas in the outlet of the dryer 14 reaches a set temperature. It comprises a step of spraying the water into the dryer 14 and drying it in the state that the set temperature of the gas in the outlet of the dryer 14 is set to be a set temperature in drying the latex, and a step of setting the set temperature of the gas in the outlet of the dryer 14 to be higher than the set temperature in drying the latex when canceling the drying of the latex and then starting the spray of the water instead of the latex.