Various commands and data are input to an image display device via an input block. Part or whole of basic image data formed of a dot matrix is stored in a basic image data storage device of the image display device. A portion of the basic image data in a display range is converted to display image data to display the display image data on the display screen, in response to a corresponding one of the various commands input by the input. From the input block, there are input a start command for starting an automatic scroll process for automatically continuously shifting the display range in a scrolling manner in a predetermined one of upward, downward, leftward and rightward directions on the basic image data, and a proportion change command for changing a proportion between the size of the display image data and the size of the basic image data, at or before the start of the automatic scroll process or during the automatic scroll process. The automatic scroll process is started in response to the start command, and the display image data is changed in response to the proportion change command and according thereto to thereby display resulting display image data on the display screen.