PROBLEM TO BE SOLVED: To provide an impedance measuring device capable of reducing a cost required for impedance measurement while ensuring the safety of a blood circuit. An impedance measuring device 150 attached to a blood circuit 110 having a needleless port 116, the measurement circuit 151, and one end having a contact portion 1141 capable of contacting a liquid in the blood circuit 110 at the other end. The first electrode 114 having an exposed portion 1142 exposed to the outside of the blood circuit 110 on the side, and the first electrode 114 having one end side of the first electrode 114 engaged with and fixed to the needleless port 116 while being inserted into the needleless port 116. The adapter electrode 152 having the first electrode holding portion 115 having a locking mechanism, and the second electrode 1531 can be removed from the first electrode 114 in a state where the second electrode 1531 and the second electrode 1531 are in contact with the first electrode 114. A measurement electrode 153 including a second electrode holding portion 1532 having a second locking mechanism for fixing to the electrode is provided. [Selection diagram] Fig. 1【課題】血液回路の安全性を担保しつつ、インピーダンス測定にかかるコストを低減できるインピーダンス測定装置を提供すること。【解決手段】ニードルレスポート１１６を有する血液回路１１０に取り付けられるインピーダンス測定装置１５０であって、測定回路１５１と、一端側に血液回路１１０内の液体と接触可能な接触部１１４１を有し他端側に血液回路１１０外に露出する露出部１１４２を有する第１電極１１４、及び第１電極１１４の一端側がニードルレスポート１１６に挿入された状態でニードルレスポート１１６と係合して固定する第１ロック機構を有する第１電極保持部１１５を備えるアダプタ電極１５２と、第２電極１５３１及び第２電極１５３１が第１電極１１４に接触した状態で第２電極１５３１を第１電極１１４に対して取り外し可能に固定するための第２ロック機構を有する第２電極保持部１５３２を備える測定用電極１５３と、を備える。【選択図】図１
