The device (100) has control circuits (124,124a) to measure blood buffer parameter of measuring unit selected from group consisting of bicarbonate concentration and carbon dioxide partial pressure. The measured value of blood buffer parameter signal is supplied to control device (125) to regulate actual value of blood buffer parameter to preset value range. The pH measuring unit (150a) is provided in upstream of dialysis unit (105) to supply pH value signal to alarm unit (130) to trigger alarm signal exceeding or falling below specific pH range.