An ion removes provided between a feed water valve for supplying water to an outer tub and a detergent supply case and an upper portion from the outer tub includes a cylindrical vessel in which sodium type strong acid positive ion exchange resin is filled up, a salt water vessel provided above the cylindrical vessel, and a salt vessel provided in the salt water vessel for receiving salt to enable plural regeneration of an ion exchange resin. Salt from the salt vessel is dissolved in water supplied to the salt water vessel and salt water having a concentration of about 10% is generated. After completion of every washing feed water cycle and every rinsing feed water cycle with an interval, the salt water is caused to flow into the ion exchange resin and the ion exchange resin is automatically regeneration-processed.