1. An image scanning apparatus, comprising: a scanner to scan a document and generate a scan image; a sensor to sense pole points on the scan image in a main scan direction, to sense vertical streak suspected pixels based on at least one of a brightness difference and a color difference between the sensed pole points and pixels surrounding the sensed pole points, and to sense vertical streaks based on a consecutiveness of the vertical streak suspected pixels in a sub scan direction; and a corrector to correct the sensed vertical streaks on the scan image.