1. A different-type-light-source photographic image determination method comprising: a first step of developing data on a target film image so as to correspond to a predetermined X-Y two-dimensional coordinate system representing a relationship between RGB average data on each constituent pixel and respective color component data, and of dividing developed pixels to a plurality of groups so that pieces of the RGB average data on the respective pixels are arranged equidistantly; a second step of operating and deriving 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 group difference sum for each of the divided groups, for each of R, G, and B; a third step of operating and deriving a thickness factor for normalizing a distribution thickness of a pixel distribution in a direction in which the pixel distribution is distanced from said reference line, for each of the divided groups; and a fourth step of operating and deriving an image difference sum by a product-sum operation between the group difference sum operated and derived in the second step and the thickness factor operated and derived in the third step, wherein if the image difference sum for the R, G, or B operated and derived in the fourth step is greater than a predetermined value, the target film image is determined as a photographic image photographed using different types of light sources.