A mask region extraction unit (11) extracts a region to be masked from a panoramic image. A mask processing unit (12) generates a panoramic image in which the region from the panoramic image to be masked is masked. An alignment unit (20) aligns the direction of a celestial image with the imaging direction of the panoramic image. A mapping processing unit (14) maps the post-mask processing panoramic image and the celestial image to a 3D panoramic space as a texture. A 3D image generation unit (16) generates a 3D panoramic image which uses the imaging location as a viewpoint, and in which the 3D panoramic space is viewed in a designated line of sight.