The present invention has an object to comprise an apparatus for high efficiency gas temperature and humidity adjustment and an adjustment method allowing to elevate the heat exchange efficiency of a cooling coil, reduce the cooling water quantity, lower also the pipe arrangement diameter and water supply pump power, making possible to cut the initial cost and running cost of the air-conditioning system. The apparatus for high efficiency gas temperature and humidity adjustment is characterized by that means for removing condensate water deposited on the cooling coil.