An instructed position, which includes an instruction area for receiving a predetermined instruction and is displayable two-dimensionally and three-dimensionally, on a display means where an instruction image is displayed is detected. Upon setting on the display means a control range corresponding to the instruction area displayed on the display means such that the control range is changed between during the two-dimensional display and during the three-dimensional display, information of a tentative instructed position is obtained by receiving an instruction directed to the instruction area during the three-dimensional display. A horizontal shift on the display means of the tentative instructed position during the three-dimensional display relative to a position of the instruction area during the two-dimensional display is calculated. The control range is changed based on the horizontal shift to make the control range coincide with a visually recognized instruction area through stereoscopic viewing during the three-dimensional display.