1. An image generation method for generating a stereoscopic panorama image, comprising: acquiring a left panorama image and a right panorama image respectively captured by a left panorama camera and a right panorama camera which are located so as to be away from each other by a prescribed distance; synthesizing a rearward image area, of a rearward area, included in the right panorama image and captured by the right panorama camera to the left panorama image, instead of a rearward image area, of the rearward area, included in the left panorama image and captured by the left panorama camera; synthesizing the rearward image area, of the rearward area, included in the left panorama image and captured by the left panorama camera to the right panorama image, instead of the rearward image area, of the rearward area, included in the right panorama image and captured by the right panorama camera; and generating the stereoscopic panorama image using the synthesized left panorama image as a left-eye image and using the synthesized right panorama image as a right-eye image.