In order to provide a data processing device and the like, capable of performing highly accurate reference correction even in a case where an object protrudes in reference channels in most of the measurement views, an image processing device (data processing device) of an X-ray CT apparatus calculates a unit air calibration reference value which is a value per unit tube current of an air calibration reference value which is reference data measured during air calibration, calculates a reference value (estimated reference value) corresponding to an X-ray condition in the main scanning on the basis of an output tube current value in the main scanning and a unit air calibration reference value, and corrects normalized reference data obtained by normalizing a measured reference value in the main scanning with the estimated reference value, to be included in an allowable error range, so as to remove the influence of protrusion.
