A planar image and a mark are displayed on a display having an outer periphery. A region is provided on the display. The region has a boundary distanced from the outer periphery of the display. The mark is moved with respect to the planar image on the display when the mark is positioned in the region. The planar image is scrolled in a direction directed from the region to the mark on the display when the mark is positioned at an outside of the region. This method allows the mark to be positioned efficiently.