An index extraction unit detects indices from a sensed image sensed by a sensing unit which senses an image of a physical space on which a plurality of indices is laid out. A convergence arithmetic unit calculates position and orientation information of the sensing unit based on the detected indices. A CG rendering unit generates a virtual space image based on the position and orientation information. A sensed image clipping unit extracts, as a display image, an image in a display target region from the sensed image. An image composition unit generates a composite image by compositing the extracted display image and the generated virtual space image. A display unit displays the composite image.