The blood purification apparatus has a control device (19) that performs a venous returning blood process S1, an arterial returning blood process S4 and a negative pressure applying process S1a. The returning of the blood is performed by substituting a physiological saline solution for the blood in the blood circuit. The negative pressure applying process S1a releases a negative pressure after applying the negative pressure to a flow route on an upstream side from an arrangement position of a blood pump 4 in the arterial blood circuit (1). The blood pump (4) is in a normal rotation and an electromagnetic valve V3 switches over the physiological saline solution supplying line 8 from a closing state to a circulating state.
