An endoscope reprocessor includes a medicinal solution tank configured to store a medicinal solution; a first detachable portion provided in the medicinal solution tank and configured to detachably hold the concentration meter such that a measuring surface of the concentration meter is placed in the medicinal solution tank; a preserving fluid tank configured to store a preserving fluid of the concentration meter; and a second detachable portion provided in the preserving fluid tank and configured to detachably hold the concentration meter such that the measuring surface of the concentration meter is placed in the preserving fluid tank.