There is provided a data processing apparatus, a printing apparatus and a data processing method, that can reduce a processing load and a processing time in reading data even in a case where null data is added to print data for correcting displacement of a printing position caused by inclination of a print head. To achieve this, there is provided a data processing apparatus including a first writing unit, a second writing unit and a reading unit. The reading unit reads out data arrays corresponding to the print target image and does not read out data arrays corresponding to outside of the print target image in the first storage unit, from a plurality data arrays stored in the second storage unit that have been written in by the second written in unit.