Disclosed is a dishwasher including, a circulating pump for pressing and then supplying wash liquid, an injection arm for permitting the wash liquid pressed and supplied from the circulating pump to be injected by a predetermined passage structure, an underdrain container for collecting the wash liquid injected from the injection arm and supplying the collected wash liquid to the circulating pump, during a washing stage, a soil collecting chamber having a micro filter with a fine mesh for ramifying and finely filtering the wash liquid supplied from the circulating pump and returning the same to the underdrain container, during the washing stage, a drain pump for allowing the wash liquid to be drained through a drain passage which is extended from the underdrain container, and through a connecting passage which is extended from the soil collecting chamber and connected to the drain passage, during a draining stage. The present invention has advantages of preventing pollution of newly supplied wash liquid from being aggravated, since foreign materials filtered by the micro filter in the washing stage is smoothly discharged in the draining stage, and removing troublesome process of additionally removing the foreign materials after dish washing, since the micro filter is self-purified, thereby improving efficiency in washing and convenience in use.