The purpose of the present invention is to perform higher precision beam hardening correction with a low calculation load, even for targets having elements of a wider range of effective atomic numbersZeff, and contribute to the presentation of a more quantitative X-ray image. At least one normalized X-ray attenuation amount is obtained for each pixel region by normalizing the X-ray attenuation amount [mu]t of two X-ray energy BINs selected from among two or more X-ray energy BINs, at least one effective atomic number is estimated for each pixel region from reference information representing the theoretical correspondence relationship between the normalized X-ray attenuation amount and the effective atomic number of an element, and the matching of at least two atomic numbers among at leastone estimated effective atomic number (ZHigh, ZLow) and the effective atomic number (Zm) pre-designated when performing beam hardening correction is determined.