PURPOSE: To always accurately remove a part of humidity from humidity- containing air without requiring the replacement of a moisture absorbing material, by replacing a part of the air recirculating in an air recirculation pipe exposed to the open air with the dry air in the atmosphere.

CONSTITUTION: An air recirculation pipe 2 whose circumference is exposed to the atmosphere 1 is provided, and air discharge holes 4 and air introducing holes 6 are provided to the peripheral wall of the pipe 2. For example, two or more small diameter holes 7 serving both as the air discharge holes 4 and the air introducing holes 6 are provided to the pipe at predetermined intervals. Air 3 containing much humidity such as the air used in the drying of clothing is recirculated in the pipe 2. Whereupon, a part of the air is discharged to the atmosphere through the air discharge holes 4 and the air 5 in a dry state in the atmosphere 1 is simultaneously introduced into the air 3 through the air introducing holes 6. A part of the air 3 containing humidity recirculated in the pipe 2 is replaced with the air 5 in the dry state to obtain such a state that a part of humidity in the air 3 is removed.