To prevent deterioration of quality when powder, slurry, or the like, to be carried is passed through a cooling/humidifying tunnel by cooling/ humidifying or drying it at an appropriate speed on a screw conveyor, or the like.

At the time of low temperature, a refrigerating machine 1 is rotated to cool brine in a heat exchanger 2 and the cooled brine is fed to the hollow section of a cooling/humidifying tunnel 5 by rotating a liquid pump 3. In order to bring about an appropriate cooling temperature on the inside, the cooling/humidifying tunnel 5 is subjected to temperature control by providing a screw conveyor for carrying powder an an optimal speed and injected with dry air or nitrogen gas in order to prevent dew formation. At the time of heating, the liquid pump 3 is rotated and a heater 40 is turned on in order to circulate heated water to the cooling/humidifying tunnel 5. Similarly to the case of low temperature, power is carried at an optimal speed in order to bring about an appropriate heating temperature on the inside of the cooling/ humidifying tunnel 5 and dry air or nitrogen gas is injected into the tunnel 5 in order to absorb moisture and gas of the discharged powder.