The present invention relates to scanning speed control device and method. The control device has judging unit and driving unit, the judging unit includes image buffer, up, and down counters, and comparator. The judging unit is used in accepting input image data, the up and down counters count the amount of input image data access by the image buffer, and the comparator decides either to increaseor to decrease the scanning speed and outputs the result to the driver. The device and the method makes it possible to control the scanning speed autoamtically.