To recognize the top and the bottom even when an original is inclined or lines described on the original are inclined by detecting the inclination amount of lines shown with document image data, preparing a histogram correcting the inclination amount from the document image data based on the inclination amount and recognizing the original direction of the document image data from the histogram.

A CPU 190 divides the resolution-converted document image data stored in a memory 180 for low resolution recognition into sections corresponding to slip-shaped areas on the original on the memory and prepares the slip-shaped histogram concerning each divided area. When the slip-shaped histogram is completely prepared, an inclination detecting processing is performed and when the inclination detecting processing is finished, the inclination histogram is prepared while using the detected inclination. When the inclination histogram is prepared, the inclination corrected histogram is acquired and while using an efficient method utilizing the histogram, exact top/bottom recognizing processing is performed.