The present invention relates to a blood purification device comprising a discharge liquid subdivision chamber for pooling a discharge liquid being discharged from a blood purification apparatus purifying blood of a patient, a first discharge liquid discharge line for causing the discharge liquid to flow through to the discharge liquid subdivision chamber, a second discharge liquid discharge line for causing the discharge liquid pooled by the discharge liquid subdivision chamber to be discharged to the exterior of the device, a discharge unit disposed on the second discharge liquid discharge line for discharging the discharge liquid pooled by the discharge liquid subdivision chamber to the exterior of the device, a residual amount detection unit for detecting the residual amount of the discharge liquid pooled by the discharge liquid subdivision chamber, a determination unit for determining, on the basis of the detection result from the residual amount detection unit, whether or not the discharge liquid amount in the discharge liquid subdivision chamber has reached a reference residual amount, and a control unit for controlling the discharge unit, wherein the control unit controls the discharge unit to execute a discharging step of discharging the discharge liquid pooled by discharge liquid subdivision chamber to the exterior of the device, and end the discharging step when the determination unit determines that the discharge liquid amount in the discharge liquid subdivision chamber has reached the reference residual amount.La présente invention concerne un dispositif de purification du sang comprenant une chambre de subdivision de liquide d'évacuation permettant d'accumuler un liquide d'évacuation qui est évacué d'un appareil de purification du sang qui purifie le sang d'un patient, une première ligne d'évacuation de liquide d'évacuation permettant d'amener le liquide d'évacuation à s'écouler à travers la chambre de subdivision de liquide d'évacuation, une seconde l
