A blood purification apparatus is provided that is capable of detecting an abnormal state of puncture into a blood vessel with an arterial puncture needle or a venous puncture needle. The blood purification apparatus includes an oscillating device 8 capable of supplying an alternating current at a predetermined frequency and changing the frequency of the alternating current among a plurality of frequencies, a measuring device 9 capable of measuring an impedance for each of the frequencies, a calculating device 10 capable of acquiring an impedance frequency characteristic, a storage device 11 capable of storing an impedance frequency characteristic acquired in a case of normal puncture into the patient's blood vessel with an arterial puncture needle a and a venous puncture needle b, and an identifying device 12 capable of identifying whether the puncture into the blood vessel with the arterial puncture needle a or the venous puncture needle b is normal in accordance with the change observed between the impedance frequency characteristic acquired by the calculating device 10 and the impedance frequency characteristic stored in the storage device 11.
