An endoscope reprocessor includes a concentration sensor including a concave section in which a sensing section is housed and a permeable membrane configured to cover the concave section, a pressure resistant container in which the concentration sensor is housed, a medicinal-solution lead-in section configured to introduce a medicinal solution into the pressure resistant container, and a pressure adjusting section 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.
