1. An image processing apparatus, comprising: input means for inputting images; storage means for storing the images input from said input means, said storage means storing a plurality of images having common partial images; characteristics extraction means for extracting characteristics of images input from the input means; determination means for determining positions of respective overlapped common partial images of the plurality of images stored in said storage means based on the image characteristics extracted in said characteristics extraction means; synthesis means for forming an image by synthesizing said plurality of images according to a result of the determination by said determination means; and output means for outputting the image synthesized by said synthesis means.