1. An X-ray imaging apparatus comprising: a X-ray generator which is configured to emit first X-rays toward a target object at a first emission angle and to emit second X-rays toward the target object at a second emission angle which is different from the first emission angle, wherein a dosage level of the second X-rays is lower than a dosage level of the first X-rays; a detector which is configured to detect the first X-rays and the second X-rays; an image processor which is configured to acquire a first X-ray image from the detected first X-rays and to acquire a second X-ray image from the detected second X-rays, of which the dosage level is lower than the dosage level of the first X-rays, and to generate a stereoscopic image by combining the acquired first X-ray image and the acquired second X-ray image; and a display which is configured to display the generated stereoscopic image, wherein the image processor is further configured to match an image quality of the first X-ray image with an image quality of the second X-ray image by improving the image quality of the second X-ray image.