PURPOSE: To design a structure so that it can easily be fabricated and also can meet scale-up requirements by separating defoaming material elements from each other in an isolated state and also in such a manner that their bottoms are at an elevated level not coming into contact with a liquid level, and their interval is made to be larger than an average foam diameter as the elements are supported by a non-capillary material.

CONSTITUTION: This defoaming device is equipped with a tank 6 filled with a foamable liquid 10 containing fine particles. A foam layer which grows on a liquid level from bubbles 7 scattered after the ejection of a gas from a nozzle under pressure, passing through piping 4 at the bottom of the tank, comes into contact with defoaming material elements 1 consisting of a capillary material which are arranged on the lower surface of branch pipes 2 for supporting and concurrently distributing a cleaning liquid which are spaced from the other on the water level. A liquid produced by defoaming drops into an area under the liquid level, and the isolated gas escapes upward passing through an area between the defoaming material elements 1. Next, if the defoaming function deteriorates, the cleaning liquid is sent under pressure to a cavity part in the defoaming material element 1 from the tiny hole of the branch pipe 2 for distributing the cleaning liquid through a main pipe 12 for distributing the cleaning liquid. The cleaning liquid spews out of the cavity part to an outer surface, and a cohesive particle layer becomes separated, dripping downward. Thus the defoaming function of the capillary material is restored.