An object of the present invention is to realize a technique capable of generating a texture image from all of polygons constructing a three-dimensional shape model without a dropout and a texture image on which an editing or correcting operation can be easily performed. When a computer reads original three-dimensional model data 51, an original three-dimensional model is set in a virtual model space, and a cylindrical plane is set as a projection plane around the original three-dimensional model. A virtual projection computing unit 14 functions to virtually project a texture image corresponding to a polygon which can be projected onto the projection plane, thereby generating a projected texture image. On the other hand, by individually extracting a unit texture image corresponding to a polygon which cannot be projected onto the projection plane, thereby generating an unprojected texture image.