A dish washer includes a sump communicated with a tub to accommodate water, a water supply pump for pumping the water in the sump, a filtering device for receiving a part of the water pumped through an auxiliary passageway to filter the pumped water and to supply the filtered water to the sump again, and a bypass for bypassing the water to be supplied to the filtering device to the tub or the sump when the filtering device is blocked by sewage. The bypass includes a first sensor detecting water passing therethrough and the filtering device being blocked and transmitting the detected result to a controller, and a second sensor detecting and informing the water pollution level to the controller when the filtering device is blocked. A controlling method thereof determines an algorithm of a cycle for washing or rinsing dishes using information acquired from the first and the second sensors.