A dishwasher including a cabinet assembly having a tub in which dishes are received, a sump, having a water collection unit configured to store wash water disposed therein, which is coupled to an interior of the cabinet assembly to collect wash water and to supply steam generated in the water collection unit into the cabinet assembly, and a heater module located outside the sump to transfer heat to the water collection unit and to heat the wash water in order to generate steam. The heater does not contact the wash water, preventing corrosion or oxidation of the heater.