A virtual object (402) and stylus model (403) as images to be composited to a real space image are rendered by changing background transparencies according to a mutual positional relationship. When the virtual object image is composited to the real space image, the image of the stylus included in the real space image is observed while reflecting the positional relationship with the virtual object. In this way, in an MR image, the depth ordering between real and virtual objects can be correctly and easily expressed.