Even when the display contents on the display screen are changed, the entire or a part of the display item is displayed, given a higher priority. When a part of image (20) is displayed in a displayable area (14 or 15) that displays a display item on a display screen, a user designates a portion, which he or she desires to keep it displayed, as a prioritized display section (21). When a change of size or the like of the displayable area (14 or 15) is recognized, in response to the change, a part of image (20, 22 or 23) is extracted so that the designated prioritized display section (21) is displayed in the displayable area (14 or 15), and then, it is placed in the displayable area (14 or 15).