1. An image synthesizing apparatus for producing a synthetic image from at least first and second images, wherein the synthetic image consists of a background image and at least a main image superimposed on the back ground image, said apparatus comprising: a first display section for displaying said at least first and second images one by one upon each of said images being selected from among images input in said image synthesizing apparatus; a second display section for displaying an outer frame and at least an inner frame located inside said outer frame; a frame selecting device for selecting one of said outer and inner frames as displayed in said second display section; a crop boundary displayed on said image in said first display section, said crop boundary having a similar shape to the frame that is selected by said frame selecting device; a frame modifying device for modifying any of said outer and inner frames by homothetically changing size or position of said crop boundary relative to the image displayed in said first display section; and a cropping and pasting device for cropping those areas of said first and second images that are each individually bounded by said crop boundary, and pasting the cropped area of said first image as the background image in said outer frame, and the cropped area of said second image as the main image in said inner frame.