The disclosed invention allows the user to move to an area to which the user desires to display in a page to which the user desires to move by a single manipulation and to allow next page/preceding page operation to be done only by a mouse operation. An area displayed on the main screen 50 is displayed on the sub-screen 51 of a reduced image of the page which is currently displayed on the main screen 50 with a rectangular view frame 60. Dragging the view frame 60 by a mouse within the page causes the display area in the main screen to move in real time. Dragging the view frame of the sub-screen 51 to a neighboring page causes the view frame 60 to be moved in the moved sub-screen. Dropping the view frame at the place on the neighboring sub-screen to which the view frame 60 moved causes the main screen to be switched to that page to display the place indicated by the view frame in the main screen. Simultaneously, the sub-screen is scrolled so that the sub-screen of the page displayed in the main screen comes to the center of the sub-screen column.