The amount of time spent extracting linear noise components is reduced, when removing linear noise components from an image. A reduced image is generated, by reducing a radiation image in at least one of the vertical and horizontal directions. A linear noise image that represents linear noise components in the Y direction is generated, by extracting linear noise components from the reduced image. Thereafter, the generated linear noise image is enlarged to the image size of the original image; the linear noise components are removed from the radiation image, employing the enlarged linear noise image.