Provided are an apparatus for processing a medical image, and a method of processing a medical image by using the apparatus. The apparatus includes: an image obtainer that receives a first image obtained by photographing an object; and an image processor that calculates a scaling factor for adjusting a magnification of the first image based on statistic information corresponding to the object and generates a second image to be displayed by normalizing a size of the object by applying the calculated scaling factor to the first image.