dialysis the blood volume maintained normally by the patient is believed to be the standard blood volume the standard blood volume is a blood volume which the patient would have if healthy by considering factors that might influence the human blood volume for example the patient 39 s age sex body height and the like defined beforehand by doctors and the like it refers to the bv volume change and it can be calculated by the following formula u03b4bv bv volume change ht at the time of the initiation of the dialysis ht at the time of the measurement u2212 1 the ht is the abbreviation of hematocrit showing the bulk ratio of red corpuscle in the whole blood it is the ratio of the bv volume change and as shown in the following formula the u03b4bv level at the time of the measurement is divided by bv 0 and is expressed in percentage u03b4bv u03b4bv bv 0 u00d7 100 it is calculated by dividing the bv level at the time of the measurement by bv 0 and is expressed in percentage bv bv level at the time of the measurement bv 0 u00d7 100 if the standard blood volume is defined the target bv at a given time point of blood purification can be calculated from the defined standard blood volume and bv 0 target bv standard blood volume primary blood volume u00d7 100 bv 0 which is the primary blood level can be calculated by a common method for example according to the hematocrit level according to the embodiment of the present invention a blood purification apparatus having excellent effects as follows can be obtained 1 the blood purification can be.