PROBLEM TO BE SOLVED: To obtain a differential phase image which removing streaky noise generated by unwrap errors.SOLUTION: A radiation imaging apparatus includes: a differential phase image producing section 40 producing a differential phase image in which pixel values are wrapped into a predetermined value range having a width α based on image data obtained by a radiation image detector an unwrapping section 41 performing a phase unwrapping processing to the differential phase image a statistical operation section 44 obtaining a mode value by statistical operation of pixel values in each subregion segmented in the unwrapped differential phase image as a processing unit in which errors caused by the phase unwrapping processing is to be corrected and a correction processing section 45 calculating, for each pixel, an integer n which allows a difference Δ between the mode and a pixel value of each pixel to satisfy nα-α/≤Δ
