1. An image synthesizing system for synthesizing more than one item of divisional image data respectively representing more than one image of more than one portion of an object, said system comprising: an input unit for inputting said more than one item of divisional image data, and for each of said more than one item of divisional image data, further inputting additional information including information indicating that said more than one item of divisional image data represents a series of images related to each other, and indicating a proper sequential order of the more than on item of divisional image data, which are to be synthesized, wherein said proper sequential order indicates relative positions of the more than one item of divisional image data at a time when photographs of the more than one item of divisional image data are taken; a synthesizing unit for synthesizing said more than one item of divisional image data in the proper sequential order automatically, based on said additional information to obtain an item of synthesized image data representing a synthesized image even when an order of the input of the more than one item of divisional image data becomes out of the proper sequential order for the series of images related to each other; and an output unit for outputting said item of synthesized image data; wherein the additional information and the more than one item of divisional image data are input independently.