Endoscopic preprocessor, a densitometer having a permeable membrane, the permeable membrane comprises a holding portion for holding the concentration systems to be positioned a predetermined water level, the chemical solution to a higher level than said predetermined level a chemical storage unit for storing, connecting the a drainage portion for discharging the chemical solution from the chemical solution reservoir, a liquid supply portion for supplying liquid to permeate membranes of the concentration meter, to the drainage unit and the liquid supply portion It is, when the chemical solution in said chemical solution reservoir portion is lower than the predetermined water level, comprising a control unit to wet the osmosis membrane by driving the liquid supply portion内視鏡リプロセッサは、浸透膜を有する濃度計と、前記浸透膜が所定の水位に配置されるように前記濃度系を保持する保持部を備え、前記所定の水位よりも高い水位まで前記薬液を貯留する薬液貯留部と、前記薬液貯留部から前記薬液を排出する排液部と、 前記濃度計の浸透膜に液体を供給する液体供給部と、前記排液部および前記液体供給部に接続されて、前記薬液貯留部内の前記薬液が前記所定の水位より低い時に、前記液体供給部を駆動して前記浸透膜を濡らす制御部と、を含む。
