When a dialysate circuit 4 is cleaned after dialysis, both opening/closing valves V101 and V102 are closed after a dialysate in the dialysate circuit 4 is replaced with a cleaning liquid. The opening/closing valve V12 is opened, and the cleaning liquid is circulated by pumps P1 and P4 while being heated by a heater H1, to clean the inside of the dialysate circuit 4. A deaeration tank 31 is provided downstream of the pump P1. Air bubbles generated from the cleaning liquid serving as hot water are deaerated by the deaeration tank 31 and are then discharged into a gas storage tank 48 via a deaeration passage 32. The pumps P1 and P4 can be reliably prevented from being unable to operate with the air bubbles generated from the cleaning liquid.
