To reduce drying time and power consumption by cooling wet air that is obtained by evaporating the water of an object to be dried, condensing water in air and reducing moisture, heating air after reducing moisture, and then circulating the air through the object to be dried.

When kitchen garbage (an object to be dried) is to be thrown and is dried, air in a drying device is heated by air-heating equipment 21 and is sent from a discharge port 30 into a treatment container 5 by an air circulation means 7 for heating the kitchen garbage. As a result, air where steam is mixed is sucked by a dehumidification drying means 2 from a suction port 29, and steam is cooled here and becomes waterdrop and is delivered to a storage bath. In a process of dehumidification and drying by the dehumidification drying means 2, when temperature around air-cooling equipment 22 and the air-heating equipment 21 rises abnormally, the temperature is detected by temperature sensors 9 and 11, a fan 26 is driven for cooling a cooler 25, and surplus heat is unloaded from the drying device.