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