A blood purification device used with a blood circuit includes an arterial-side line and a venous-side line attached to a blood purifier to which, at the ends thereof, the arterial-side line and the venous-side line are connected, the blood purification device including: a supply line connected to a supply unit which supplies a priming fluid, and which is capable of being connected to a leading end of the venous-side line； a discharge line connected to a discharge unit 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 which is disposed upon the arterial-side line. By driving the blood pump in a state of the supply line being connected to the venous-side line and the discharge line being connected to the arterial-side line, the blood circuit and the blood purifier are primed.
