PURPOSE: To enable the effective utilization of drain, by arranging a defoaming means to prevent the generation of foam in a steam chamber.

CONSTITUTION: A concentration apparatus A is constituted of a receiving tank 2 for receiving a waste liquid 1, a steam pipe chamber 4 arranged to the upper part to said chamber and having a steam pipe 3 for heating the waste liquid vertically provided therein, an evaporation chamber 6 comprising a waste liquid falling cylinder 5 communicating the receiving chamber 2 and the steam pipe chamber 4, a supply tank 7 for supplying the waste liquid 1 to the receiving chamber 2, a recirculation pump 8 for recirculating the waste liquid 1 to the steam pipe chamber 4 from the evaporation chamber 6 and the receiving chamber 2 through the waste liquid falling cylinder 5, a drain tank 12 for receiving drain 11 discharged from the steam pipe 3 of the steam pipe chamber 4 which receives and compresses steam generated in the evaporation chamber 6 and stores the same as compressed steam 9 and a concentrate tank 14 for receiving the concentrate 13 of the waste liquid 1 discharged from the evaporation chamber 6 while the waste liquid 1 is concentrated in said evaporation chamber 6. A defoaming means 16 to prevent the waste liquid 1 from generating foam is arranged in said evaporation chamber 6.