PURPOSE: To remove dust with a simple method and prevent the exertion of bad influence due to the dust by striking a dust containing discharging gas against a foam producing surface producing many foams and sticking the dust in the dust containing discharging gas to the foam to separate.

CONSTITUTION: A foam producing solution supply part 3 spouts a foam producing solution 8 through a nozzle 31 from the upper end of upstream side of a gas passable foam producer 2 into a double structural meshlike body of the foam producer 2 and at first the dust is stuck to the foam and next, the foam apart from the meshlike body, to which the dust is stuck, is, after liquefied in the rear meshlike body, made foam by the force of the discharging gas. In this case, a part is recovered as a liquid in a storage tank part 5 without turning into foam and the foam scattered as the dust containing foam is guided by a guiding member 4 and is dropped to the direction of the storage tank part 5 and stored, which is defoamed by the force of the discharging gas forcibly blown in the guiding member 4 through tends to make foam groups and is mixed with the foam producing solution 8 stored in the bottom.