An opening-and-closing body configured to open and close an opening moves across a first section in which the opening-and-closing body moves in the closing direction against its own weight and a second section in which the opening-and-closing body moves in the closing direction according to its own weight. The driver drives the opening-and-closing body in the closing direction continuously from the first section to the second section. The predictor predicts that the drive section of the opening-and-closing body will shift from the first section to the second section when the driver drives the opening-and-closing body in the closing direction toward the second section from the first section. The drive controller decreases the driving output of the driver for driving the opening-and-closing body in the closing direction according to the result of the prediction made by the predictor.