1. A mixed reality space image generation method for generating a mixed reality space image formed by superimposing virtual space image onto a real space image obtained by capturing a real space, comprising: a first image superimposing step of superimposing a first virtual space image onto a real space image based on an occlusion by a real object; and a second image superimposing step of superimposing a second virtual space image onto the superimposed image generated in the first image superimposing step without considering the occlusion.