The objective of the present invention is to provide a blood purifying device with which it is possible to suppress discharge quantity errors attributable to variations in the suction pressure of a blood pump.This blood purifying device is provided with: a blood circuit 1 capable of causing the blood of a patient to circulate outside the body； a dialyser 2 which is connected to the respective base ends of an arterial blood circuit 1a and a venous blood circuit 1b, and which purifies blood that is circulating outside the body through the blood circuit 1； a squeezed tube C connected to the arterial blood circuit 1a； a blood pump 3 which is capable of causing liquid in the squeezed tube C to flow by squeezing the squeezed tube C in the longitudinal direction while compressing the squeezed tube C in the radial direction； and a pressure detecting means 10 which is attached to a specific part of the arterial blood circuit 1a closer to the distal end 1aa thereof than the position in which the blood pump 3 is disposed, and which is capable of detecting the suction pressure of the blood pump 3； wherein the blood purifying device is additionally provided with a control means 12 capable of controlling the drive speed of the blood pump 3 in accordance with the suction pressure of the blood pump 3 as detected by the pressure detecting means 10.L'objet de la présente invention est de fournir un dispositif de purification du sang permettant de supprimer des erreurs de quantité de refoulement pouvant être attribuées à des variations dans la pression d'aspiration d'une pompe d'assistance circulatoire. Ce dispositif de purification du sang comprend : un circuit sanguin 1 permettant d'amener le sang d'un patient à circuler jusqu'à l'extérieur du corps ； un dialyseur 2 qui est relié aux extrémités respectives de base d'un circuit de sang artériel 1a et d'un circuit de sang veineux 1b, et qui purifie le sang qui circule jusqu'à l'extérieur du corps à travers le circuit sanguin 1 ； un
