The ink jet printing apparatus, wherein, to print images on a printing medium, a plurality of print heads, each of which includes an ejection port array provided by arranging multiple ink ejection ports in a widthwise direction of the printing medium, are arranged in a conveying direction of the printing medium, including: a unit for detecting a printing position displacement with respect to a printing position of a reference print head on the printing medium for each of remaining print heads excluding the reference print head which is one of the plurality of print heads; and a unit for adding non-image data corresponding to the printing position displacement to print data to be printed by the plurality of print heads, so as to align the printing positions of the plurality of print heads.