PURPOSE: To remove much smaller particles in a cyclone dust collector by providing a steam feeding means for feeding steams to gas, and a cooling means installed downstream of the steam feeding means and for cooling the gas into which steam is fed from the steam feeding means.

CONSTITUTION: In a dust collector where gas to be given dust collection 13A is introduced into a cyclone 17 and particles in the gas 13A are removed by using centrifugal force generated on the particles in the gas 13A in the cyclone 17, steam 14C is fed to the gas 13A by a steam feeding means 14. And by a cooling means 16 installed downstream of the steam feeding means 14, the gas 13A into which steam is fed by the steam feeding means 14 is cooled. As a result, the gas 13A is oversaturated to condense the steam around the particles included in the gas 13A. In this way, particles of small mass of ≤0.1μ turn into those of apparent large mass by the condensation of the steam 13C to allow the removal of the particles.