1. A line noise eliminating apparatus, includes: an image binarizing device which generates a binary image by binarizing an input image that includes a line noise; a line noise reliability calculating device which rotates the binary image by a plurality of rotation angles to generate respective rotated images, calculates an edge feature quantity for each of black-pixel consecutive areas in the rotated images, and calculates line noise reliability based on the edge feature quantities; a line noise area determining device which selects, based on the line noise reliability, a rotation angle candidate with which a direction of the line noise becomes consistent with a prescribed direction from the rotation angles, and determines a line noise area of the respective rotated images that correspond to each of the rotation angle candidates based on the line noise reliability; a density converting device which generates a density-converted image by applying local image enhancement on an area that corresponds to the line noise area of the input image so as to convert the density into density of pixels that correspond to the input image; and an image synthesizing device which generates a synthesized image by synthesizing the density-converted images that correspond to each of the rotation angle candidates, when there are a plurality of the rotation angle candidates.