To provide an air cleaning device of high performance capable of capturing and eliminating even hydrophobic contaminants by water.

A humidifying space B increasing its water molecular concentration to at least an oversaturated state or a near-oversaturated state, is formed inside a main body casing 2, and the air including contaminants a, a, ..., such as chemical substances and fine particles is introduced into the humidifying space B to be mixed with the water molecules, so that water molecular clusters c, c, ..., are formed around the contaminants a, a, ..., and they are discharged after cooled to be liquid droplet of lower than a dew point by a cooling means 16. Thus, the effect of eliminating even the hydrophobic contaminants can be sufficiently improved.