Disclosed a dishwasher, wherein dishes placed on a conveyor are washed, rinsed, and dried while being sequentially conveyed to a washing chamber, a rinsing chamber, and a drying chamber, the dishwasher including: a heat exchanger allowing hot air to be supplied to the drying chamber by heat exchange; a wash water tank in which water supplied to the washing chamber or the rinsing chamber is stored; and a spray device spraying water supplied from the wash water tank onto the dishes placed on the conveyor, whereby it is possible to save energy by providing a single heat exchanger to preheat wash water and rinse water and supply hot air to the drying chamber, and to improve circulation of wash water by a filtering device applied to a structure for reusing wash water, thereby improving sanitation of dishwashing.