A medical imaging apparatus includes an X-ray radiation unit configured to radiate X-rays onto an object and onto a calibration phantom, which does not overlap the object, according to a first irradiating condition for a pre-shot; a detector configured to detect the X-rays having passed through the object and through the calibration phantom; and a controller configured to acquire calibration information by using a pre-shot image acquired from the detected X-rays, and determine a second irradiating condition for main imaging by using the calibration information.