A control method for an endoscope reprocessor is a control method for an endoscope reprocessor that includes a treatment tank, a circulation conduit that links a circulation opening and a discharge opening opened in the treatment tank to each other, a first pump that feeds liquid from the circulation opening towards the discharge opening, an atmospheric open conduit including a first end portion open to an atmosphere and a second end portion connected between the circulation opening and the first pump in the circulation conduit, a filter that filtrates a liquid flowing from the treatment tank through the circulation opening into the circulation conduit, and a sensor that detects a liquid feeding state in the circulation conduit, where the liquid feeding state in the circulation conduit is measured by the sensor during operation of the first pump in a state where the inside of the atmospheric open conduit is closed.
