An X-ray imaging system for preventing deterioration in image quality of a phase contrast image due to streak noise occurred in a direction corresponding to a signal line of an X-ray image detector. The X-ray imaging system is composed of an X-ray source, first and second absorption-type gratings, and a flat panel detector (FPD). Image captures are performed with the second absorption-type grating moved in X direction orthogonal to its grating line, relative to the first absorption-type grating. The FPD has pixels arranged in the X direction and Y direction orthogonal to the X direction. A group of the pixels arranged in the X direction are connected to a single signal line that reads out charge. A differential phase image producing section produces a differential phase image based on pieces of image data obtained from the respective image captures. A phase contrast image producing section integrates the differential phase image, produced by the differential phase image producing section, in a direction corresponding to the signal line of the FPD to produce a phase contrast image.
