The purpose is to perform, in a blood purification device in which a transfusion line for supplying a transfusion such as anticoagulant is connected to a blood removal line, automatic blood return without performing reverse rotation of a blood pump and without providing a transfusion supply unit for blood return on a side downstream of the blood pump. A control unit 80 of a blood purification device 1 stops operation of a blood pump 30 and a transfusion pump 52, opens a first transfusion line 40 by means of a first opening/closing valve 42, and closes a blood removal line 10 by means of a second opening/closing valve 11； performs forward rotation of the blood pump 30 by a predetermined volume X to move the first transfusion from the first transfusion line 40 to the blood removal line 10； performs reverse rotation of the transfusion pump 52 by a predetermined volume Y to move the first transfusion in the blood removal line 10 to the second transfusion line 50； closes the first transfusion line 40 by means of the first opening/closing valve 42 and opens the blood removal line 10 by means of the second opening/closing valve 11； and performs forward rotation of the transfusion pump 52 by a predetermined volume Z to move the first transfusion in the second transfusion line 50 to the blood removal line 10 and return the first transfusion to the patient P. The device achieves automatic blood return to the patient P.
