PROBLEM TO BE SOLVED: To provide a blood purifier enabling a self-analysis step accurately, even when selectively using either wet type blood purifying means or dry type blood purifying means.SOLUTION: A blood purifier comprises control means C enabling a self-diagnosis step in which the quality of a connection state of a blood circuit is diagnosed based on a detection value of pressure detection means, which is changed by forming a closed circuit including a connection position of the pressure detection means in a blood circuit, and by pressurizing the inside of the closed circuit. In the blood purifier, a dialyzer 3 is used in such a manner that either wet type blood purifying means whose inside is pre-filled with a filling liquid or dry type blood purifying means which is not filled with the filling liquid is arbitrarily and selectively used. The control means C diagnoses the quality of the connection state of the blood circuit in the self-diagnosis step according to the type of the dialyzer 3 connected to the blood circuit.SELECTED DRAWING: Figure 1
