In a high print resolution, high image quality mode and a low print resolution, high speed mode, image processes are made in common between them to the extent possible, and the same gradation characteristics and image densities can be obtained between them. For this purpose, for the high image quality mode, a dot arrangement pattern is prepared for a pixel region having gradation data of K levels, which determines the presence or absence of print dots at K-1 areas, and in which the printing of 1 dot is permitted at all of the K-l areas. On the other hand, for the high speed mode, a dot arrangement pattern which determines the presence or absence of print dots at a number of areas less than K-1 is prepared, and in which the sum of the number of dots permitted to be printed at the pixel region is K-1.