A blood purification apparatus includes a blood circuit having arterial and venous blood circuits, a blood pump, a blood purifying device, an indicator applying device that applies a predetermined indicator to the blood flowing extracorporeally through the blood circuit, a detecting device that detects the indicator applied by the indicator applying device, an arithmetic device that calculates, based on the indicator detected by the detecting device, a recirculation rate, and a calculating device that calculates an ideal extracorporeally circulating blood flow that results in the recirculation rate being no more than a predetermined value when the recirculation rate calculated by the arithmetic device is greater than the predetermined value. The recirculation rate is a proportion of a recirculated blood flow, which is reintroduced to the patient from the venous blood circuit and directed again to the arterial blood circuit, relative to an extracorporeally circulating blood flow.
