[Object] To provide a blood purification apparatus which can suppress air bubbles from flowing to a distal end of an arterial blood circuit during an arterial returning blood process and can reduce the burden on health care workers. [Solution] The blood purification apparatus includes a control device 19 that can perform a venous returning blood process S1 in which returning of blood is performed by substituting a physiological saline solution for blood from a connection portion connected to a physiological saline solution supplying line 8 to a distal end of a venous blood circuit 2 in a blood circuit during returning of blood an arterial returning blood process S4 in which the returning of blood is performed by substituting the physiological saline solution for the blood from the connection portion connected to the physiological saline solution supplying line 8 to a distal end of an arterial blood circuit 1 in the blood circuit and a negative pressure applying process S1a for releasing a negative pressure after applying the negative pressure to a flow route of an upstream side from an arrangement position of a blood pump 4 in the arterial blood circuit 1, by allowing the blood pump 4 to be in a normal rotation and causing an electromagnetic valve V3 to switch over the physiological saline solution supplying line 8 from a closing state to a circulating state.
