1. A radiation tomographic image generating apparatus comprising: an actual measurement image reconstruction unit for carrying out image reconstruction of a plurality of actual measurement projection data acquired from different directions with respect to an inspection object including a high radiation absorber, to generate an actual measurement reconstruction image; a high absorber area identifying unit for identifying a high absorber area of the actual measurement projection data from the actual measurement projection data and the actual measurement reconstruction image, to acquire high absorber area identification data; a data replacing unit for carrying out, using the high absorber area identification data, data replacement of the high absorber area of the actual measurement projection data with data obtained from pixels adjacent the high absorber area, to acquire replacement projection data; a replacement image reconstruction unit for carrying out image reconstruction of the replacement projection data to generate a replacement reconstruction image; a difference processing unit for determining a difference between the actual measurement projection data and the replacement projection data to acquire difference projection data; a difference image reconstruction unit for carrying out image reconstruction of the difference projection data to generate a difference reconstruction image; and a composite image generating unit for generating a composite reconstruction image by selecting at least one image from among the actual measurement reconstruction image, the replacement reconstruction image and the difference reconstruction image on an area-by-area basis.