A water softener is provided to generate a water softening effect by soft water and an ozone effect by dissolved ozone at the same time by injecting ozone into a hot water tank and a cold water tank. A water softener comprises a housing and a pump(15). The housing has ion-exchange resins(1,2) stored therein. The housing has water flown therein such that the water is reacted with the ion-exchange resins to flow out softened water from the housing. The pump injects air outside the housing into the housing. The water softener agitates the ion-exchange resins and a regenerating material regenerating the ion-exchange resins by air injected by the pump.
