To eliminate the wastewater of cleaning water by recycling the wastewater discharged without being influenced by the form of processes before washing, to reduce a purchase cost, and to provide a system for recycling the cleaning water which can perform the treatment efficiently at a low cost and a method for wastewater treatment.

The wastewater discharged from the first rinsing process 12c is supplied around seed ice formed from water of prescribed purity or above which is arranged in a freezing separator 18 and cooled gradually so that only water in the wastewater is frozen by using the seed ice as a nucleus. While the impurities of the wastewater is left unfrozen, only the frozen water is transferred to an ice storage tank 30 and melted. The water is separated into filtrate and concentrated water through ion exchange, and the filtrate is used as regenerated cleaning water.