An X-ray imaging device includes an X-ray irradiation module, an X-ray detection module and an image processor. The image processor is configured to perform: acquiring a high-energy image and a low-energy image respectively obtained by X-ray of relatively high-energy and X-ray of relatively low-energy; generating high-energy frequency component images for each of a plurality of frequency bands by decomposing the high-energy image; generating low-energy frequency component images for each of a plurality of frequency bands by decomposing the low-energy image; generating merged frequency component images by merging at least a portion of the high-energy frequency component images for each of the plurality of frequency bands and at least a portion of the low-energy frequency component images for each of the plurality of frequency bands; and generating a standard image using the merged frequency component images.