A blood purification apparatus includes a blood circuit, a blood purifying device, a first valve, a discharge line, a second valve, and a detection device. The blood circuit has an arterial blood circuit and a venous blood circuit. The first valve opens and closes the venous blood circuit. The second valve opens and closes the discharge line. The detection device detects whether a priming solution is replaced with blood in an end portion of the venous blood circuit at an upstream side from the first valve. The blood purification apparatus automatically turns the first valve from a closed position to an open position and the second valve from an open position to a closed position, respectively, when the detection device detects the priming solution being replaced with the blood.