An ion-exchange apparatus includes a raw-water tank 1, a treatment section, an ion exchanger and a hydrophilic layer. The raw-water section contains a liquid to be treated with impurity ions. The treatment tank 2 contains a treatment material with exchange ions exchangeable with the impurity ions. The ion exchanger 3 enables the passage of the impurity ions from the raw-water tank 1 to the treatment tank 2 and the passage of the exchange ions from the treatment tank 2 to the raw-water tank 1. The hydrophilic layer M, with a water contact angle of 30° or less, is disposed on at least a surface of the ion exchanger adjacent to the treatment tank 2.