The endoscope reprocessor according to the present invention includes a chemical tank that stores chemical liquid, a concentration measurement unit that is disposed in the chemical liquid tank so that a permeable membrane is submerged in the chemical liquid, and vaporizes a part of the chemical liquid. A gas generating unit that generates a gas, the gas generating unit disposed at a position where the gas floating in the chemical solution contacts the osmotic membrane, and the gas generating unit connected to the concentration measuring unit and the gas generating unit； A control unit that performs a first control for driving the concentration measurement unit while the unit is stopped and a second control for driving the concentration measurement unit while the gas generation unit is driven. 本発明の内視鏡リプロセッサは、薬液を貯留する薬液タンクと、浸透膜が前記薬液中に水没するように前記薬液タンクに配置される濃度測定部と、前記薬液の一部を気化してガスを発生させる気化部を含み、前記薬液中で浮上した前記ガスが前記浸透膜に接触する位置に配置されるガス発生部と、前記濃度測定部および前記ガス発生部に接続され、前記ガス発生部を停止した状態で前記濃度測定部を駆動する第１制御と、前記ガス発生部を駆動した状態で前記濃度測定部を駆動する第２制御と、を行う制御部と、を含む。
