By using an ink jet head, which has for each color two parallel columns of nozzles arranged side by side in the main scan direction and shifted from each other by one-half the pitch at which the nozzles are arranged in each column, odd-numbered rasters and even-numbered rasters making up an image are printed by the two nozzle columns. The registration between the odd- and even-numbered rasters is secured during the printing to produce an image with high print quality. For that purpose, the ink ejection timing between the two raster groups is shifted by a predetermined interval to form a plurality of adjustment patterns; the adjustment patterns printed are checked and, according to the check result, an adjustment value for the ink ejection timing between the two ink nozzle columns is entered, and the entered adjustment value is stored to be reflected on the actual printing operation. To facilitate the adjustment pattern check, the plurality of adjustment patterns have a dot distribution with a blue noise characteristic at a resolution at which the printing apparatus can print.