1. A stereoscopic viewing image generation apparatus, comprising: a stereoscopic viewing image generation means for generating, using a three-dimensional medical image representing a subject as input, a stereoscopic viewing image for stereoscopic output of the subject based on a given image generation condition; and a non-stereoscopic viewing image generation means for generating a non-stereoscopic viewing image for non-stereoscopic output equivalent to the stereoscopic output based on the three-dimensional medical image and the image generation condition of the stereoscopic viewing image.