A dialysis system which does not need to use a physiological saline in replenishing a solution or cleaning and priming the dialysis system, does not need a troublesome setting operation and can easily and accurately set a flow rate of a replenisher solution. The dialysis system includes a closed type water-removal control apparatus 1, a dialyzer 2, a fresh dialysate line 3 as well as a used dialysate line 4, a dialysate pressurizing line 5, a dialysate pressurizing pump 51 provided in the dialysate pressurizing line 5, an artery side blood line 6, a blood pump 61 provided in the artery side blood line 6 and a vein side blood line 7. According to the dialysis system, by pressurizing a dialysate into a communication line of the dialysate, the dialysate is made to flow from a dialysate flow path 21 into a blood flow path 22 through a dialysis membrane 23 of the dialyzer 2 and the inside of a blood circulation path can be cleaned and primed.