1. A character recognition preprocessing method in a character recognition preprocessing apparatus, the method comprising the steps of: detecting a character string region including a character string from an image, and dividing the character string region into character regions corresponding to respective characters constituting the character string in the character string region; extracting upper feature points and lower feature points for each character region; generating an upper boundary line connecting the upper feature points and a lower boundary line connecting the lower feature points; determining a layout of a reference region; dividing a real character string region, which is formed by the upper and lower boundary lines and includes the character string, into correction character regions corresponding to the respective characters, based on the upper and lower feature points; mapping an upper boundary line of each correction character region to an upper reference straight line of the reference region by interpolation, and mapping a lower boundary line of each correction character region to a lower reference straight line of the reference region by interpolation; and applying an interpolation value used in the mapping to respective pixels included in each correction character region, thereby mapping each character region to the reference region.