The invention provides a plate discharging device and a plate discharging method. The plate discharging device comprises a 90-degree plate rotating mechanism, a discharging conveying line, a discharging robot, a jacking transferring mechanism, a wrong material storage station, a plate centering mechanism, a moving stopping mechanism and a control module, and the 90-degree plate rotating mechanism, the discharging conveying line, the discharging robot, the jacking transferring mechanism, the wrong material storage station, the plate centering mechanism and the moving stopping mechanism are all electrically connected with the control module. According to the plate discharging device, through the automatic production process, the plate production efficiency is improved, manual participation in production is reduced, the quality loss caused by manual operation can be reduced, and the labor cost is reduced.