1. A method for processing a scanned image, comprising: a shaded region extracting step of extracting a region, which is shaded by a shading object and lies in a margin in vicinity of an edge of the scanned image, as a shaded region; a pixel value repairing step of repairing values of pixels, which lie both in a line segment and the shaded region, by using a linear model according to known values of pixels, which lie both in the line segment and the margin, the line segment passing through the shaded region and being parallel to the edge; estimating noises of pixels, which lie both in the line segment and the shaded region, according to values of known noises of pixels, which lie both in the line segment and the margin, the line segment passing through the shaded region and being parallel to the edge; and adding the estimated noises to the repaired values of the pixels which lie both in the line segment and the shaded region.