1. A computer-readable storage medium having stored therein an image display program which stereoscopically displays a real world image onto which a 3-dimensional virtual object is superimposed, on a screen of a stereoscopic display apparatus capable of providing a stereoscopic view, by using outputs from a real camera imaging section for a right eye and a real camera imaging section for a left eye, the image display program causing a computer to function as: position orientation calculation means for recognizing a predetermined shooting target in each of pieces of real world image data respectively outputted from the real camera imaging section for a right eye and the real camera imaging section for a left eye, and calculating position orientation information indicating relative positions and relative orientations of the real camera imaging section for a right eye and the predetermined shooting target with respect to each other, and position orientation information indicating relative positions and relative orientations of the real camera imaging section for a left eye and the predetermined shooting target with respect to each other; position orientation integrating means for integrating the two pieces of position orientation information calculated by the position orientation calculation means, thereby calculating one piece of position orientation information; virtual camera setting means for determining the position and the orientation of a right virtual camera for generating a virtual image for a right eye, and the position and the orientation of a left virtual camera for generating a virtual image for a left eye, in a predetermined virtual space, based on the one piece of position orientation information integrated by the first position orientation integrating means; right virtual space image generation means for generating a right virtual space image indicating the predetermined virtual space as it is looked at from the right virtual camera; left virtual space image generation means for generating a left virtual space image indicating the predetermined virtual space as it is looked at from the left virtual camera; and display control means for superimposing the right virtual space image onto the piece of real world image data outputted from the real camera imaging section for a right eye, and superimposing the left virtual space image onto the piece of real world image data outputted from the real camera imaging section for a left eye, to output images for a stereoscopic view to the stereoscopic display apparatus.