PROBLEM TO BE SOLVED: To provide a blood purifying apparatus, which can check connection failures or the like of a blood circuit on priming, prevents air entertainments on automatic priming by a wet-type blood purifier, and is improved in a function to discharge filling liquid in the blood purifier.SOLUTION: The blood purifying apparatus includes the blood purifier 1, the blood circuit 2, a blood pump 3, an artery side valve V1 provided upstream of the blood pump 3, a priming liquid supply line 4 connected between the blood pump 3 and the artery side valve V1, a liquid discharge line 6 equipped with a valve V7, an artery chamber 24, a vein chamber 25, and a valve V2 provided downstream of the vein chamber 25, in which an air induction line 5 is provided so as to connect the vein chamber 25 and the artery chamber 24, and a Y-tube 61 is provided so as to intercommunicatably connect an artery side puncture needle connection end 27 and a vein side puncture needle connection end 28 to the liquid discharge line 6 and be connectable to a liquid discharge path 62.
