Blood purification apparatus

A blood purification apparatus that includes a blood purifier, an interior of which is divided into a blood flow path and a dialysis fluid flow path by a blood purification membrane, a blood circuit having an artery passage and a vein passage connected to the blood flow path of the blood purifier, a dialysis fluid circuit having a dialysis fluid supply passage and a dialysis fluid retrieval passage connected to the dialysis fluid flow path of the blood purifier, a blood pump provided for the artery passage, a replenishment fluid supply passage connected to the dialysis fluid supply passage, a fluid replenishment passage connected to the blood circuit, an online port which is coupled with the replenishment fluid supply passage and to and from which the fluid replenishment passage can be attached and detached, a water removal passage connected to the dialysis fluid retrieval passage, and a water removal pump provided for the water removal passage,

• the online port comprises an inner port connecting the replenishment fluid supply passage to the fluid replenishment passage and an outer port having a tubular shape and being provided around the inner port, and
• further provided are a first bypass passage allowing a space formed between the inner port and the outer port to communicate with the dialysis fluid supply passage;
• and an open/close valve configured to open and close the first bypass passage, wherein
• in a fluid draining procedure to eliminate fluid remaining in the blood circuit, by opening the open/close valve on the first bypass passage and discharging fluid from the dialysis fluid retrieval passage by using the water removal pump, air is caused to flow into the first bypass passage through the outer port, and the air is further caused to flow via the dialysis fluid supply passage through the replenishment fluid supply passage toward the blood circuit, so that fluid is thereby removed from the fluid replenishment passage.