This invention provides a blood-purifying device, which can suppress the error alarming and detect precisely the abnormal conditions of patient or device during the treatment of blood purification.The blood purifying device of the present invention, comprising : a blood circuit 1 formed by a blood circuit of artery side 1a provided at its leading end with a piercing needle a of arterial side, and a blood circuit of venous side 1b provided at its leading end with a piercing needle b of vein side； a blood pump 3； a dialyzer 2 for purifying the blood flowing in the blood circuit 1； a venous pressure sensor 5 for detecting the pressure of patient blood flowing in the blood circuit of venous side 1b； a venous pressure monitoring means 12 used to provide alarming based on the comparison of a reference blood pressure value, which is defined by the detected value of said venous pressure sensor 5 or by the predicted value upon the detection, with a predetermined alarming value, wherein said venous pressure monitoring means 12 can update said alarming value at each predetermined timing.提供一種血液淨化裝置，可以抑制誤警報，同時正確地檢測血液淨化治療中的患者和裝置的異常狀況。在血液透析裝置中，靜脈壓監視器(12)每隔規定時間更新警報值，該血液透析裝置包括：血液回路(1)，由在前端安裝了動脈側穿刺針(a)和靜脈側穿刺針(b)的動脈側血液回路(1a)和靜脈側血液回路(1b)所構成；血液泵(3)；透析器(2)，對流過血液回路(1)的血液進行淨化；靜脈壓感測器(5)，可檢測從靜脈側血液回路(1b)流過的患者的血液的壓力；靜脈壓監視器(12)，將該靜脈壓感測器(5)檢測出的壓力或被檢測時預測的壓力作為基準值，與規定的警報值進行比較來進行警報。
