To solve a problem of a conventional image processing unit where deterioration in image quality has been remarkable in a reproduced image because there are extracted parts and non-extracted parts in one character when thick parts and thin parts are in existence in the character in the image area separation and because a block-shaped image pattern may be wrongly extracted on the occurrence of mis-extraction in the image patterns.

First a shadow extract section 11 extracts an area with high gray level from input image data, a dot extract section 12 extracts an area consisting of dots, and a line segment extract section 13 extracts line segments with a width by a 1st prescribed number of pixels. Then a small area extract section 14 extracts an area with a width by a 2nd prescribed number of pixels from each area extracted by the shadow extract section 11 and the dot extract section 12, and a line segment correction section 15 corrects the line segments extracted by the line segment extract section 13 on the basis of the extracted area.