Both calcified areas and a tumor mass area are displayed with high resolution in the depth-direction, thereby improving the diagnosis accuracy. Radiographic images for different imaging directions taken by applying radiation to a subject from the different imaging directions are obtained, and a plurality of first tomographic images having a first slice thickness are generated based on the obtained plurality of radiographic images and a plurality of second tomographic images having a second slice thickness that is greater than the first slice thickness are generated based on the radiographic images. Then, MinIP processing is applied to the first tomographic images to generate a MinIP image, and MIP processing is applied to the second tomographic images to generate a MIP image. Then, combining processing is performed using the MinIP image and the MIP image to generate a composite image.
