1. An image component separation device comprising: component separating means for separating more than one image components from more than one radiographic images inputted thereto, the image components respectively representing more than one predetermined components in a subject, each radiographic image being formed by radiation transmitted through the subject, each radiographic image representing degrees of transmission and attenuation through the subject of each of different patterns of radiation having different energy distributions, the component separating means separating the image components by calculating weighted sums using predetermined weighting factors for each corresponding pixel among the radiographic images; and band extracting means for extracting, from each of the radiographic images, an image component of a spatial frequency band containing the predetermined components, wherein the component separating means carries out independent component analysis on the image components of the spatial frequency band extracted by the band extracting means to obtain separation factors for separating the more than one image components from the image components of the spatial frequency band and uses the separation factors as the predetermined weighting factors.