1. A tomographic image generation device comprising: a radiographic image obtaining unit for obtaining radiographic images for different imaging directions taken by applying radiation to a subject from the different imaging directions; a tomographic image generation unit for generating a plurality of tomographic images of the subject based on the plurality of radiographic images obtained by the radiographic image obtaining unit; a compression processing unit for applying compression processing in a direction perpendicular to slice planes of the tomographic images to the tomographic images generated by the tomographic image generation unit to generate compressed tomographic images; an imaging direction range obtaining unit for obtaining a range of the imaging directions; and a compression rate setting unit for setting a compression rate of the compression processing based on the range of imaging directions obtained by the imaging direction range obtaining unit.