To provide a desalting method and apparatus for purifying water- quality wherein the amount of anion resin, used for removing impurities at the time when water purification is carried out by removing injected chemical agents for adjusting water-quality and impurities utilizing ion-exchange resins, can be reduced.

The supply water or the raw water before the treatment is fed to two cathion resin columns 1 thereby the injected chemical agents for water-quality adjustment as well as the impurities are removed. Subsequently, raw water is supplied from the cathion column 1 into two small capacity mixed- bed type desalting columns 2 containing cathion resin and anion resin thereby the remaining impurities are removed. The cathion column 1 and the mix-bed type desalting columns 2 are respectively regenerated in cycles which are independent of each other.