A densitometer 15 having a concave part containing the sensing part and a osmotic membrane 10 closing the concave part, a pressure vessel 20 containing the densitometer 15, a chemical liquid introduction part 21 for introducing the disinfectant R into the pressure vessel 20, And a pressure adjusting unit 25 that adjusts the pressure so that the internal pressure of the concave portion is lower than the internal pressure of the pressure vessel 20.センシング部を収容した凹状部及び凹状部を塞ぐ浸透膜１０を有する濃度計１５と、濃度計１５が収容された耐圧容器２０と、耐圧容器２０に消毒液Ｒを導入する薬液導入部２１と、凹状部の内圧が耐圧容器２０の内圧に比べて低くなるように圧力を調整する圧力調整部２５と、を具備する。
