The present invention provides a blood purification apparatus capable of assuredly preventing the blood of a patient from being extracorporeally circulated through a blood circuit with a puncture needle being inappropriately stuck in an access vessel. A blood purification apparatus according to the present invention includes a blood circuit (1) through which blood of a patient extracorporeally circulate, and a dialyzer (2) that purifies the blood flowing in the blood circuit (1). The apparatus further includes a pressure-change-producing device capable of applying a positive pressure or a negative pressure to distal portions of the blood circuit (1) while an arterial puncture needle (a) and a venous puncture needle (b) are yet to be connected to the blood circuit (1), a pressure-change-detecting device capable of detecting pressure changes in the distal portions of the blood circuit (1) that occur when the distal portions of the blood circuit (1) that are under the positive pressure or the negative pressure applied by the pressure-change-producing device are connected to the arterial puncture needle (a) and the venous puncture needle (b) that are stuck in the patient, and an evaluation device (11) capable of evaluating a state of sticking of the arterial puncture needle (a) and the venous puncture needle (b) on the basis of the pressure changes detected by the pressure-change-detecting device.
