An endoscope reprocessor includes a concave treatment tank 11 in which an endoscope is disposed, a lid 21 that covers the treatment tank 11, an air-open conduit 31 that is connected with the treatment tank 11 and opens the treatment tank 11 to air, a gas filter connection part 35 disposed on the air-open conduit 31, an on-off valve 34 disposed closer to the treatment tank than the gas filter connection part 35 on the air-open conduit 31, a pressure sensor 41 that detects an internal pressure of the treatment tank 11, a pressurizing unit 51 that is disposed closer to the treatment tank than the on-off valve 34 on the air-open conduit 31 or connected with the treatment tank 11 and pressurizes the treatment tank 11 even when the on-off valve 34 is closed, and a control unit 61 that controls the on-off valve 34 and pressurizing unit 51.
