Provided is a blood purification device which, without undergoing preparatory operation, is capable of readily supplying a dialysis solution from a dialysis solution introduction line to a blood circuit to perform fluid replacement during ultrafiltration treatment, or readily supplying a dialysis solution from the dialysis solution introduction line to the blood circuit to perform reinfusion after the ultrafiltration treatment. Specifically provided is a blood purification device which is equipped with a dialyzer 1 for purifying blood flowing through a blood circuit, a dialysis solution introduction line L1 capable of introducing a dialysis solution to the dialyzer 1, a dialysis solution ejection line L2 capable of ejecting drainage from the dialyzer 1, and a water-removal pump 10 capable of removing water from the blood flowing through the blood circuit, and which enables fluid replacement or reinfusion by supplying dialysis solution from the dialysis solution introduction line L1 to the blood circuit, wherein when ultrafiltration treatment is carried out in which the introduction of dialysis solution to the dialyzer 1 is stopped while the water-removal pump 10 is driven to remove water, delivery of the dialysis solution to the dialyzer 1 is performed while restricting the inflow of the dialysis solution.La présente invention concerne un dispositif de purification du sang qui, sans subir d'opération préparatoire, est apte à alimenter facilement une solution de dialyse à partir d'une conduite d'introduction de solution de dialyse à un circuit sanguin pour exécuter le remplacement de liquide durant le traitement d'ultrafiltration, ou à alimenter facilement une solution de dialyse à partir de la conduite d'introduction de solution de dialyse au circuit sanguin pour exécuter la réinfusion après le traitement d'ultrafiltration. La présente invention concerne particulièrement un dispositif de purification du sang qui comprend un dialyseur (1) pour purifier le sang s'écou
