An endoscope reprocessor includes a concentration sensor 15 including a concave section in which a sensing section is housed and a permeable membrane 10 configured to cover the concave section, a pressure resistant container 20 in which the concentration sensor 15 is housed, a medicinal-solution lead-in section 21 configured to introduce a medicinal solution R into the pressure resistant container 20, and a pressure adjusting section 25 configured to adjust pressure such that an internal pressure of the concave section is low compared with an internal pressure of the pressure resistant container 20.
