A data generation apparatus for generating image data used for printing an image on a print medium by using a printing apparatus having an adjusting function for increasing and/or decreasing a conveyance amount by which the print medium is conveyed in a conveyance direction with respect to a standard conveyance amount used when an image with a specified size is printed includes an acquisition unit configured to acquire an adjustment amount of the conveyance amount, and a changing unit configured to change a size of the image data corresponding to the conveyance direction of the print medium according to the adjustment amount acquired by the acquisition unit.