A dishwasher includes a dishwashing tub in which dishes are washed; a first tank configured to store therein cold washing water to be used for a next stroke; and a second tank configured to store therein hot washing water, which has been used in the dishwashing tub. The second tank is placed adjacently to the first tank to transfer heat from the stored hot washing water to the cold washing water. An opening is configured to deliver the hot washing water to the dishwashing tub; and a circulation pipe is configured to connect the dishwashing tub and the second tank to enable the hot washing water to circulate between the second tank and the dishwashing tub. A circulation valve is configured to allow the hot washing water to pass therethrough or to block the hot washing water from passing therethrough.