Abstract: A data processing device is applied to an X-ray system which irradiates an object with continuous X-rays and processes data detected by a photon counting X-ray detection device. An n-dimensional vector corresponding to each of “n” energy regions set a spectrum of the continuous X-rays is calculated for each detector pixel based on the data. For each search region virtually set up based on one or more detector pixels, the n-dimensional vectors at the detector pixels belonging to each search pixel are mutually vector added in the n-dimensional space. The n-dimensional representative vector representing each of the plurality of search regions is calculated. Based on the representative vectors and an unit region having a desired size virtually set in a material space with coordinate information of the degree of attenuation of the X-rays, the information indicating the amount, type and properties of the material of the object is obtained.