A water softener which uses ion exchange resins to soften water and a washing machine having the same are disclosed. The water softener and the washing machine having the same include an ion exchange unit including ion exchange resins therein, the ion exchange unit including a first ion exchange unit and a second ion exchange unit which alternately perform softening of water and regeneration of the ion exchange resins. Since any one of the first ion exchange unit and the second ion exchange unit performs softening of water and the other one thereof performs regeneration of the ion exchange resins, it is possible to continuously supply soft water.