Provided are a blood purification device and method with which it is possible to reduce the amount of blood anticoagulant. A blood purification device (1) for withdrawing blood and then returning the purified blood, wherein the blood purification device (1) comprises: a blood circulation circuit (2) having a blood purifier (20) for dialysing blood in order to reduce waste products and for feeding dialysed blood from the outside a blood pump (30) for transferring blood within the blood circulation circuit (2) and an anticoagulant introduction device (60) for mixing in blood a blood anticoagulant (62) that prevents coagulation of blood. The blood purifier (20) is disposed under negative pressure at the upstream side of the blood pump (30).
