1. An apparatus for generating an image file for use in a stereographic display, comprising: a file obtaining means which obtains a main image file in which a main stereographic image is recorded and a sub-image file in which a sub-stereographic image is recorded; image composing means which generates a first synthetic stereographic image by reconstructing the sub-stereographic image to conform to a main stereographic image and synthesizing the reconstructed sub-stereographic image with the main stereographic image, and generates a second synthetic stereographic image by reconstructing a main stereographic image to conform to a sub-stereographic image and synthesizing the reconstructed main stereographic image with the sub-stereographic image; and a file generating means which generates a file of a predetermined format including the first and second synthetic stereographic images.