1. A radiographic image analysis device that analyzes a subject image of a subject obtained by radiography to estimate a body thickness distribution of the subject, the device comprising: a memory storing computer executable instructions; and a processor configured to execute the stored instructions, which when executed by the processor cause the processor to perform the following operations: acquire the subject image; acquire a virtual model of the subject having a predetermined body thickness distribution; generate a composite image by combining an estimated primary X-ray image and an estimated scattered X-ray image, wherein the estimated primary X-ray image is obtained by X-ray radiography of the virtual model, wherein the estimated scattered X-ray image is obtained based on the X-ray radiography of the virtual model, and wherein the generated composite image serves as an estimate of the X-ray radiographic image of the subject; correct the body thickness distribution of the virtual model such that a difference between the estimated image and the subject image is reduced; and determine the corrected body thickness distribution of the virtual model as the body thickness distribution of the subject.