1. A video combining method for superimposing a virtual image generated by a computer on the real world observed by a user, comprising the steps of: inputting an image obtained by image sensing the real world; inputting position and orientation information of the user's view point; generating a virtual image based on said position and orientation information; extracting a virtual image elimination area of said virtual image; and combining said virtual image with said image obtained by image sensing based on said virtual image elimination area.