Provided are an X-ray imaging apparatus that is capable of tracking a position of an object of interest using a Kalman filter so as to reduce the amount of X-ray radiation exposure of a subject, calculating covariance indicative of accuracy of the tracing, and controlling a collimator so that the position of the object of interest and calculated covariance may be correlated with a position and an area of a region into which X-rays are radiated, and a method of controlling the X-ray imaging apparatus.