1. An apparatus for processing a medical image, the apparatus comprising: an image obtainer that receives a first image including an object; a memory that stores a representative value of object size, the representative value being determined based on at least one of an age including gestational age, a photographed region, and an item of the object; an image processor that calculates a scaling factor based on the representative value and a size of the object to be displayed when the size of the object is the representative value, and generates a second image having the calculated scaling factor by adjusting a magnification of the first image; and a display that displays the second image.