Provided is a blood purification device 10, which is used with a blood circuit 100 which includes an arterial-side line LA and a venous-side line LV attached to a blood purifier 110 to which, at the ends thereof, the arterial-side line LA and the venous-side line LV are connected, said blood purification device 10 comprising: a supply line LS which is connected to a supply unit 12 which supplies a priming fluid, and which is capable of being connected to a leading end of the venous-side line LV； a discharge line LD which is connected to a discharge unit 14 which discharges the priming fluid after use, and which is capable of being connected to a leading end of the arterial-side line； and a blood pump PB which is disposed upon the arterial-side line LA. By driving the blood pump PB in a state of the supply line LS being connected to the venous-side line LV and the discharge line LD being connected to the arterial-side line LA, the blood circuit 100 and the blood purifier 110 are primed.
