Image processing apparatus and method of calculating distance information and size information of an object within an image frame are provided. The method of processing an image includes: sequentially moving a focus lens from infinity to a short distance; overlapping and storing frames including an object focused at each movement location of the focus lens; and displaying a synthesis frame that synthesizes the overlapped frames in one frame, and simultaneously, calculating relative distance information of objects focused at different locations of the focus lens based on an object focused at an arbitrary location of the focus lens, and displaying the relative distance information in the synthesis frame.