PURPOSE: To attain multiwidow display and scaling display for moving and expanding/contracting an image in displaying.

CONSTITUTION: A line memory 22 writes and successively reads out the image data of one line read out from a random port of an input memory 21. A selector 20 switches and selects image data supplied from the external and image data supplied from the line memory 22. Images already written in the memory 21 and images supplied from the external as image data are stord in the memory 21.