To provide phase contrast images of uniform image quality regardless of the inclination of small gratings.

A first absorption type grating 21 comprises a plurality of small gratings 21a-21e arrayed along a virtual cylindrical surface whose center axis is a virtual line C passing through an X-ray focus 11a. A second absorption type grating 22 comprises a plurality of small gratings 22a-22e arrayed along a virtual cylindrical surface which is coaxial with the cylindrical surface and has a radius larger than that of the cylindrical surface. A scanning mechanism 23 scans the second absorption type grating 22 in a y direction orthogonal to the virtual line C. The radiographic system includes a pitch correction amount storage part 25 for storing the correction of a scanning pitch corresponding to the inclination angle of the small gratings 22a-22e to the scanning direction for each segment corresponding to the small gratings 22a-22e. A phase differential image generation part 24 corrects the scanning pitch using a correction amount for each segment, calculates the phase deviation of the intensity change of pixel data with the corrected scanning pitch as a reference, and thus generates the phase differential image of a subject.