To easily iconize windows by automatically iconizing various widows present on a screen by dragging arbitrary places in areas of title bars of the windows to arbitrary parts at upper and lower, and right and lower ends on the screen faster than a certain speed.

The user selects the title bar 60 of a desired window 50 to be iconized with a mouse and drags it to an arbitrary place at the upper, lower, right, or left end on the screen faster than the certain speed. At this time, the speed for the iconization is previously set on a setting screen. The place where the icon of the iconized window 50 is set on the setting screen to an arbitrary place of the upper, lower, right, or left end on the screen, or the right lower part (arrayed in order from the left to the right) on the screen. Then the dragging speed is faster than the set speed and the pointer is moved to the end of the screen, the window is iconized.