PROBLEM TO BE SOLVED: To accurately measure a water removal amount with a simple configuration.SOLUTION: A blood purification device comprises: a blood purifier 120； a waste liquid pipe conduit 130 including a first branch path 131, a second branch path 132, and a third branch path 133； a dialysate pipe conduit 142； a replacement fluid pipe conduit 152； a first pump 160 that pumps out waste liquid 138 flowing through the first branch path 131 and dialysate 141 flowing through the dialysate pipe conduit 142 so that flow rates of the waste liquid and the dialysate are equal to each other； a second pump 161 that pumps out waste liquid 138 flowing through the second branch path 132 and replacement fluid 151 flowing through the replacement fluid pipe conduit 152 so that flow rates of the waste liquid and the replacement fluid are equal to each other； a third pump 162 that is connected to the third branch path 133 and pumps out waste liquid 138 flowing through the third branch path 133； a first valve 179 that opens/closes the third branch path 133； a first refuge pipe 134 through which waste liquid 138 temporarily flows； and a scale 139 that measures weight of waste liquid discharged from the waste liquid pipe conduit 130.SELECTED DRAWING: Figure 1【課題】簡易な構成で除水量を正確に測定する。【解決手段】血液浄化器１２０と、第１分岐路１３１、第２分岐路１３２および第３分岐路１３３を含む排液管路１３０と、透析液管路１４２と、補液管路１５２と、第１分岐路１３１を流れる排液１３８と透析液管路１４２を流れる透析液１４１とを互いに等しい流量で送り出す第１ポンプ１６０と、第２分岐路１３２を流れる排液１３８と補液管路１５２を流れる補液１５１とを互いに等しい流量で送り出す第２ポンプ１６１と、第３分岐路１３３に接続され、第３分岐路１３３を流れる排液１３８を送り出す第３ポンプ１６２と、第３分岐路１３３を開閉する第１バルブ１７９と、排液１３８が一時的に流れる第１退避管１３４と、排液管路１３０から排出された排液の重量を測定する秤１３９とを備える。【選択図】図１
