The present invention relates to use of the information relating to the object of the real world to achieve a variety of image representation. By extracting the image of the display device and the playing field 18 from A captured image, obtains the position coordinates of the play field 18 and the screen 174 in the world coordinate system. And in virtual space defined in the world coordinate system, the virtual world as on the opposite side of the actual world 172 across the screen 174, the ground of virtual world 170 on the surface flush with the playfield 18 in the real world 172 is positioned to build a 170. And a position corresponding to the user's point of view in real space position the virtual viewpoint 9, and generates an image obtained by projecting the virtual world 170 as a display image on the screen 174 based thereon. .The 11