1. An image processing apparatus comprising: a processing means for obtaining a processed image data set by performing further image processing on an image data set, on which image processing has been performed according to an image processing mode set at a photography device and to which supplementary information including image processing information indicating the image processing mode has been attached; an intention judgment means for judging whether an image processing mode of a processing object image data set has been intentionally set, based on supplementary information of the processing object image data set and supplementary information attached to at least one of image data sets, which were obtained before or after photography time of the processing object image data set, wherein the at least one of image data sets includes an image data set obtained immediately before obtainment of the processing object image data set; an undoing means for undoing the image processing which has been performed on the processing object image data set if the judgment by the intention judgment means is NO; and a control means for controlling the processing means so that the processing means performs the further image processing on the processing object image data set, of which image processing has been undone by the undoing means.