A tomography apparatus includes an image processor configured to obtain a first image, which is a partial image of an object, by using data obtained from a first angle section corresponding to a first point, and to obtain a second image, which is a partial image of the object, by using data obtained from a second angle section corresponding to a second point subsequent to the first point; and a controller configured to obtain first information representing a brightness change, to obtain second information representing a rate of change in a Hounsfield unit (HU) value between the first point and the second point based on the first information, and to determine a tomography start point of the object based on the second information.