PROBLEM TO BE SOLVED: To provide a blood purifier enabling priming efficiently and in a short time by allowing an alternate filling step to be performed selectively in accordance with which type of blood purifying means is used: a wet type or a dry type.SOLUTION: A blood purifier comprises a control means C which in a step of filling a priming liquid into a blood flow path of a dialyzer 3, makes a dialysate be introduced into a dialysate flow path from a dialysate introducing line according to an amount of the priming liquid, and thereby allows an alternate filling step in which the blood flow path and the dialysate flow path can be alternately filled. In the blood purifier, the 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 allows the blood purifier to determine whether to perform a concurrent filing step in priming according to the type of the dialyzer 3 connected to a blood circuit.SELECTED DRAWING: Figure 1
