A waste fluid treating apparatus including a pure water generating unit including an ion exchanger for purifying a fresh water sent by a fresh water pump to obtain a pure water. The ion exchanger includes a housing, an anion exchange resin layer accommodated in the housing, and a mixed resin layer accommodated in the housing. The anion exchange resin layer is composed of only anion exchange resin, and the mixed resin layer is composed of a mixture of anion exchange resin and cation exchange resin. The housing is provided with a fresh water inlet for introducing the fresh water into the anion exchange resin layer and a pure water outlet for discharging the pure water from the mixed resin layer.