To enable the removal of soil of a filter provided on a water sucking side whenever a pump stops operation to reduce time and labor of filter cleaning by providing an air chamber and a discharging electromagnetic valve in a discharging side of the pump.

When a power of a washing machine is on and a start button is pushed, a water supply electromagnetic valve 1 and a discharging electromagnetic valve 4 are opened, and a tap water is supplied to a washing tank through a water sucking port 2. At this time, a part of the supplied water flows in a pump 7 through a discharging hose 3 as a priming. Thereafter, when the water supplying electromagnetic valve 1 is closed and the pump 7 is operated, remaining water of a bath is sucked through a water sucking hose 10 and discharged in the washing tank through the discharging hose 3. When the water in the washing tank reaches a specified amount, the discharging electromagnetic valve 4 is closed, and air in an air chamber 6 is compressed by the remaining water continuously discharged from the pump 7. When the pump 7 is stopped, warm water in the air chamber 6 flowing reversely by the pressure of the compressed air, thereby soil adhered to a filter 11 is washed down.