1. An X-ray imaging apparatus comprising: an X-ray source configured to irradiate X-rays to an object; an X-ray detector configured to obtain a first X-ray image of the object by detecting the X-rays having passed through the object; an image processor configured to perform image processing on the first X-ray image, and to create a second X-ray image; and a display configured to display the second X-ray image, wherein the image processor comprises: a noise-reduced image creator configured to generate a noise-reduced image in which a noise is reduced from the first X-ray image; a noise image creator configured to generate a noise image based on differences between the first X-ray image and the noise-reduced image; an edge image creator configured to generate, from the noise image, an edge image in which edges are enhanced; and an output image creator configured to combine the noise-reduced image with the edge image to generate a second X-ray image.