PROBLEM TO BE SOLVED: To provide an intermittent infusion method for preventing the lowering of blood, and a blood purifying apparatus.SOLUTION: The blood purifying apparatus includes a blood purifier 1, a blood circuit 2, a blood pump 3 provided in the blood circuit 21 on the upstream side of the blood purifier 1, a venous chamber 23 provided in the blood circuit 22 on the downstream side of the blood purifier 1, a dialyzing fluid supply circuit 41, and a drain circuit 42. An infusion line 5 (called on-line) for connecting the dialysing fluid supply circuit 41 and the blood circuit 21 on the upstream side of the blood pump 3 is provided, and automatic on-off valves V2 and V1 are respectively provided in the infusion line 5 and the blood circuit 21 on the upstream side of the connection part 51 with the fluid replenishing line 5, while pressure measuring means 24 is provided in the blood circuit 21 on the upstream side of the automatic on-off valve V1.
