PURPOSE: To eliminate the lowering of washing efficiency caused by foamed solution by heating foamed solution generated when a material to be washed is washed by using a detergent to weaken its surface tension while expanding air in bubbles to break them.

CONSTITUTION: Shower nozzles 12 which are arranged so that washing water 13 may be jetted for washing a material to be washed 14 to which a detergent is stuck and which is carried in and a washing water storage tank 11 which is arranged for storing washing water containing the stuck detergent after washing under the nozzles are provided. Further, a defoaming tank 18 into which foamed solution 16 formed in the upper layer of stored washing water 15 in the washing water storage tank 11 after washing is introduced from a passage 17 and which is provided with a heater 20 for heating the introduced foamed solution 23 to defoam it is provided. Thereby the introduced foamed solution 23 from the washing water storage tank 11 side is heated by the heater 20 to weaken its surface tension while expanding air in bubbles to break them, causing defoaming to be performed.