PROBLEM TO BE SOLVED: To provide a blood purification device which can relatively easily cope with even in the case where a liquid solution in use is needed to be switched in the process of treatment.SOLUTION: This blood purification device 80 includes: a blood pump 81 for sending blood on an arterial side circuit to a blood purifier a dialysate pump 82 for sending dialysate solution on a dialysate circuit to the blood purifier a waste liquid pump 83 for sending out waste solution on a waste solution circuit a first pump 84 for sending first liquid on a first circuit to a vein side circuit, a second pump 85 for sending second liquid on a second circuit to the vein side circuit and a control part 90 which controls the drive of these pumps. The control part 90 has a pump drive determination part F5 which determines whether the second pump 85 drives according to whether the first pump 84 drives.
