PURPOSE: To realize interaction wherein the display state of an image needs to be changed fast in the image display device of a computer system which has an image display means such as a CRT.

CONSTITUTION: Display data of two systems which are outputted from an image information storage means 1 and an image information storage means 2 where a display position can be specified independently of the means 1 are outputted by being selected by a data selecting means 4 according to output data from a display control information storage means 3 where a display position can be specified independently of the image information storage means 1 and 2. A control means 5 performs control for the transfer of an image to the image information storage means 1 and 2, the drawing of a figure, and the transfer of shape information to the display control information storage means 3.