A dishwasher comprising: a tub which accommodates a washing object; a sump which is disposed under the tub and stores washing water; a spray arm which sprays the washing water into the tub ; a washing pump which pumps the washing water stored in the sump to the spray arm ; a check valve which is disposed between the sump and the washing pump and openable in a direction of the washing pump from the sump by a water flow generated by operation of an impeller of the washing pump ; a heater for heating the washing water to generate steam in the washing pump ; and a draining pump for draining the washing water stored in the sump to the outside, wherein the washing pump comprises: a housing , wherein the impeller is rotatable in the housing ; and a washing water intake pipe through which the washing water flows into the housing , wherein the check valve is opened by rotating a lower portion thereof around an upper portion thereof, wherein the check valve is configured such that a part of a lower portion of the washing water intake pipe is open when the check valve is closed, wherein the check valve is closed when the heater generates steam and wherein the heater is coupled to a lower side of the washing pump , wherein the check valve is opened when the impeller rotates and preferably wherein the check valve is closed when the impeller does not rotate, wherein the check valve is configured to allow the washing water to flow from the washing pump to the sump during operation of the draining pump . a tub which accommodates a washing object; a sump which is disposed under the tub and stores washing water; a spray arm which sprays the washing water into the tub ; a washing pump which pumps the washing water stored in the sump to the spray arm ; a check valve which is disposed between the sump and the washing pump and openable in a direction of the washing pump from the sump by a water flow generated by operation of an impeller of the washing pump ; a heater for heating the washing water to generate steam in the washing pump ; and a draining pump for draining the washing water stored in the sump to the outside, wherein the washing pump comprises: a housing , wherein the impeller is rotatable in the housing ; and a washing water intake pipe through which the washing water flows into the housing , wherein the check valve is opened by rotating a lower portion thereof around an upper portion thereof, wherein the check valve is configured such that a part of a lower portion of the washing water intake pipe is open when the check valve is closed, wherein the check valve is closed when the heater generates steam and wherein the heater is coupled to a lower side of the washing pump , wherein the check valve is opened when the impeller rotates and preferably wherein the check valve is closed when the impeller does not rotate, wherein the check valve is configured to allow the washing water to flow from the washing pump to the sump during operation of the draining pump . a housing , wherein the impeller is rotatable in the housing ; and a washing water intake pipe through which the washing water flows into the housing , wherein the check valve is opened by rotating a lower portion thereof around an upper portion thereof, wherein the check valve is configured such that a part of a lower portion of the washing water intake pipe is open when the check valve is closed, wherein the check valve is closed when the heater generates steam and wherein the heater is coupled to a lower side of the washing pump , wherein the check valve is opened when the impeller rotates and preferably wherein the check valve is closed when the impeller does not rotate, wherein the check valve is configured to allow the washing water to flow from the washing pump to the sump during operation of the draining pump . <EOS>