An ink jet printing apparatus that performs printing by using a print head unit including a plurality of print heads (71, 72) for the same color, in each of which a first nozzle array (71a, 72a) formed by arranged first nozzles for forming a first size of dots on a print medium and a second nozzle array (71b, 72b) formed by arranged second nozzles for forming a second size of dots on the print medium are provided, the first size being larger than the second size, the second nozzle array being arranged along the first nozzle array, respective plurality of the first and the second nozzle arrays being arranged in a direction intersecting an array direction of the nozzles in each nozzle array, and different print heads being arranged so that respective parts of the plurality of nozzle arrays of the different print heads have print regions on the print medium which are overlapped with each other along the array direction, said apparatus being characterized by comprising: a distributing unit configured to distribute, for each print head, print data for printing dots into first data used for printing by the first nozzles provided in a print head and second data used for printing by the second nozzles provided in the same print head, said first and second data having a complementary relation with each other; and a determining unit configured to determine, for the data used for printing by the respective parts of the nozzle arrays of each of the first and second print heads which have the overlapped print regions, a ratio between amount of the data used for printing by a first combination (71a, 71b) of the first and second nozzle arrays in the first print head and a second combination (72a, 72b) of the first and second nozzle arrays in the second print head, said ratio defining a further complementary relation between the first combination and the second combination, and the combination of each of the first and second print heads consisting of the first and second nozzle arrays in which positions of respective ends of the nozzles of the respective parts of the nozzle arrays in the array direction are identical to each other and which are provided in the same print head. a distributing unit configured to distribute, for each print head, print data for printing dots into first data used for printing by the first nozzles provided in a print head and second data used for printing by the second nozzles provided in the same print head, said first and second data having a complementary relation with each other; and a determining unit configured to determine, for the data used for printing by the respective parts of the nozzle arrays of each of the first and second print heads which have the overlapped print regions, a ratio between amount of the data used for printing by a first combination (71a, 71b) of the first and second nozzle arrays in the first print head and a second combination (72a, 72b) of the first and second nozzle arrays in the second print head, said ratio defining a further complementary relation between the first combination and the second combination, and the combination of each of the first and second print heads consisting of the first and second nozzle arrays in which positions of respective ends of the nozzles of the respective parts of the nozzle arrays in the array direction are identical to each other and which are provided in the same print head.