An X-ray image processing system that processes an X-ray image using a processing apparatus that includes a processing unit that processes data and a storage unit, the processing unit comprising: an acquisition unit configured to acquire a plurality of pieces of X-ray transmission amount data provided by a plurality of sensors; an image generation unit configured to determine a material of an image in pixel unit from a difference between the plurality of pieces of X-ray transmission amount data thus acquired and generates a color image indicating material information and density information from the X-ray transmission amount data provided by the plurality of sensors, wherein the sensors comprise a high energy data X-ray sensor and a low energy data X-ray sensor, wherein the color image is generated in which the material information is a color type and the transmission amount data is a color density; a recognition unit configured to recognize articles in pixel unit based on the color image thus generated; and a synthesis unit, configured to synthesize a background image and an article image using the X-ray transmission amount data for the same background obtained by photographing a tray or a bag, wherein the generated color image and the X-ray transmission amount data are stored in the storage unit, wherein information of the articles included in the same luggage as a unit of the background is stored in the storage unit, wherein the synthesis unit is configured to generate a color image by synthesizing a luggage image and the article image using the X-ray transmission amount data, from the information of the articles stored in the storage unit and an arrangement position of the article image such as a rotation angle and starting point coordinates thereof, wherein the synthesis unit is characterized in that it is further configured to, when articles overlap, approximate a change in the X-ray transmission amount data by calculating the transmission amount using the transmission amounts acquired by the different sensors, and wherein the synthesis unit is configured to perform synthesizing by adding articles one by one in such a way that the synthesis for a first article is performed using an image of only the tray or the bag and the article image. an acquisition unit configured to acquire a plurality of pieces of X-ray transmission amount data provided by a plurality of sensors; an image generation unit configured to determine a material of an image in pixel unit from a difference between the plurality of pieces of X-ray transmission amount data thus acquired and generates a color image indicating material information and density information from the X-ray transmission amount data provided by the plurality of sensors, wherein the sensors comprise a high energy data X-ray sensor and a low energy data X-ray sensor, wherein the color image is generated in which the material information is a color type and the transmission amount data is a color density; a recognition unit configured to recognize articles in pixel unit based on the color image thus generated; and a synthesis unit, configured to synthesize a background image and an article image using the X-ray transmission amount data for the same background obtained by photographing a tray or a bag, wherein the generated color image and the X-ray transmission amount data are stored in the storage unit, wherein information of the articles included in the same luggage as a unit of the background is stored in the storage unit, wherein the synthesis unit is configured to generate a color image by synthesizing a luggage image and the article image using the X-ray transmission amount data, from the information of the articles stored in the storage unit and an arrangement position of the article image such as a rotation angle and starting point coordinates thereof, wherein the synthesis unit is characterized in that it is further configured to, when articles overlap, approximate a change in the X-ray transmission amount data by calculating the transmission amount using the transmission amounts acquired by the different sensors, and wherein the synthesis unit is configured to perform synthesizing by adding articles one by one in such a way that the synthesis for a first article is performed using an image of only the tray or the bag and the article image.