A system is provided for obtaining parameters about the position and orientation of a camera, where the camera has a fixed position and orientation, by using the image coordinates and world coordinates of markers included in an image photographed by the camera. This system uses a live-image display mode for successively obtaining images input to the camera and a still-image display mode for obtaining an image input to the camera at predetermined time. The markers can be extracted by using the image obtained in either mode. The system can select either automatic-extraction mode or manual-extraction mode for extracting the marker in live images, so that the markers can be extracted with a high degree of accuracy under all conditions to obtain the position and orientation parameters of the camera.