This invention includes a different-type-light-source image determination unit for determining whether the target film image is a different-type-light-source photographic image based on RGB component data on each of pixels that constitute data on the target film image, an image data development unit for developing data on the target film image so as to correspond to a predetermined X-Y two-dimensional coordinate system representing a relationship between a minimum of the RGB component data on the each pixel and the RGB component data for the minimum if the target film image is determined as the different-type-light-source photographic image, and a minimum difference sum operation unit for operating and deriving, from the developed data, an average of dissociations of the respective pixels relative to a reference line representing characteristics of a film image photographed by a standard light as a minimum difference sum at least for each pixel group of R, G, or B, wherein if the minimum difference sum for the pixel group of the R, G, or B operated and derived by the minimum difference sum operation unit is greater than a predetermined reference value, the target film image is determined as a photographic image of a structure having different colors.