Position and orientation information indicating the relative position and orientation relationship between the viewpoint of the observer and a physical space object on a physical space is acquired. A virtual space image is generated based on the acquired position and orientation information, and is rendered on a memory. A physical space image of the physical space object is acquired. By rendering the acquired physical space image on the memory on which the virtual space image has already been rendered, the physical space image and the virtual space image are combined. The obtained composite image is output.