A control method of an endoscope reprocessor is a control method of an endoscope reprocessor including a chemical liquid tank, a concentration measurement chamber, and a concentration meter disposed in the concentration measurement chamber, wherein a chemical liquid is introduced into the chemical liquid tank A step II of introducing the chemical solution into the concentration measuring chamber and measuring the concentration of the chemical liquid a step of draining the chemical solution in the chemical solution tank from the endoscope reprocessor, A step III of maintaining the empty state for a predetermined time, and a step IV of maintaining the moisture amount in the concentration measuring chamber above the predetermined value during the step III.内視鏡リプロセッサの制御方法は、薬液タンク、濃度測定室、および前記濃度測定室に配置された濃度計を含む内視鏡リプロセッサの制御方法であって、前記薬液タンクに薬液を導入するステップIと、前記濃度測定室に前記薬液を導入して前記薬液の濃度を測定するステップIIと、前記薬液タンク内の薬液を前記内視鏡リプロセッサから排液して、前記薬液タンク内が空となった状態を所定時間維持するステップIIIと、前記ステップIIIの間、前記濃度測定室内の水分量を所定値以上に維持するステップIVと、を含む。
