[Problem] To provide a blood purification device that can perform an operation and task that are in accordance with the final stage of retransfusion. [Solution] The blood purification device is equipped with: a blood circuit that can circulate patient blood out of the body from the tip of an artery-side blood circuit (1) to the tip of a vein-side blood circuit (2) a dialyzer (3) that purifies blood flowing through the blood circuit and a replacement liquid supply means that can supply replacement liquid into the blood circuit. Retransfusion is performed by replacing the replacement liquid supplied from the replacement liquid supply means after treatment and the blood within the blood circuit. The blood purification device is provided with: a blood distinguishing means (13, 14) that is disposed at a predetermined position in the artery-side blood circuit (1) or the vein-side blood circuit (2) and that can detect the presence/absence of blood flowing through the artery-side blood circuit or the vein-side blood circuit at the predetermined position and a recognition means (17) that can recognize the final stage of retransfusion, which is the state at which the end of replacement by replacement liquid is near, on the basis of the presence/absence of blood detected by the blood distinguishing means (13, 14) during retransfusion.La présente invention a pour but de proposer un dispositif de purification de sang qui peut réaliser une opération et une tâche qui sont conformes à létape finale de retransfusion. A cet effet, selon linvention, le dispositif de purification de sang est équipé de : un circuit sanguin qui peut faire circuler le sang dun patient hors du corps de la pointe dun circuit sanguin côté artère (1) à la pointe dun circuit sanguin côté veine (2) un dialyseur (3) qui purifie le sang sécoulant à travers le circuit sanguin et un moyen de fourniture de liquide de remplacement qui peut fournir un liquide de remplacement dans le circuit sanguin. Une retransfusio
