1. A printing control method of generating print data to be supplied to a print unit, wherein the print unit comprises a print head having a plurality of nozzles for ejecting ink, and is capable of selectively forming one of N types of dots each having different sizes at one pixel area with the print head, N being an integer equal to or greater than 2, the printing control method comprising: a dot data generation step of generating dot data based on an image data, the dot data representing a state of dot formation at each pixel, wherein the dot data generation step has a first printing mode in which the dot data for an ink type is generated as dot data using the N types of dots, and a second printing mode in which the dot data for the ink type is generated as dot data using a part of the N types of dots other than at least one of the N types of dots, wherein ink volumes for the used part of the N types of dots is respectively substantially same as ink volumes for corresponding types of dots used in the dot data for the ink type to be generated in the first printing mode.