A hemodialysis apparatus 1 includes: opening means 43 which opens a sealed dialysate circuit 4 to the outside, in the dialysate circuit 4 a storage container 48 of a dialysate, which is provided further downstream than the opening means 43 and stores therein a fresh dialysate passing through the dialysate supply passage 23 and an auxiliary power source 6 for operating the replenishing liquid pump 61, a blood pump 14 and the opening means 43. When a power failure or the like has occurred, a control means 1a is set to an auxiliary power source retransfusing mode, and then makes the auxiliary power source 6 operate the opening means 43 and the replenishing liquid pump 61 to send the fresh dialysate stored in the storage container 48 to a blood circuit 3 through a replenishing liquid passage 5. Accordingly, the hemodialysis apparatus can quickly retransfuse blood into a patient even when the power failure has occurred during dialysis treatment.
