1. An image synthesization method, whereby a plurality of images, each of which has a partially overlapping image area, are synthesized to create a single synthetic image, comprising: (A) a determination step of inputting a plurality of image data sets that correspond to said plurality of images that are input, and of determining whether or not an image in said partially overlapping image area of each of images that are indicated by said plurality of image data sets includes mainly characters; (B) an image processing step of performing, for said plurality of image data sets that are input, image processing in consonance with a result of a determination performed at said determination step; and (C) an image synthesization step of synthesizing images that are indicated by the resultant plurality of image data, for which said image processing has been performed at said image processing step.