PROBLEM TO BE SOLVED: To provide a blood purification apparatus enabling an operator to macroscopically inspect whether blood has coagulated in a mesh of a vein chamber by stopping a blood pump when a venous pressure increased, reversely filtering almost the same amount of dialysate as the volume from a blood purifier to the vein chamber and replacing the blood in the vein chamber by the dialysate.SOLUTION: The blood purification apparatus includes: a blood purifier 1 a blood circuit 2 a blood pump 3 provided on an artery side blood circuit 21 a vein chamber 23 provided on a vein side blood circuit 22 and a dialysate circuit 4. A viscous chamber 5 is provided on the dialysate circuit 4 so that hermetically sealing water-removal control can be executed. The viscous chamber 5 is equipped with a viscous pump 61, and is configured so that reverse filtration can be executed by controlling drive and stop of the viscous pump 61 having functions of a reverse filtration pump as a constituent of the reverse filtration device 6 by a reverse filtration pump control means 62.
