Image data which defines an ink amount to be ejected from each of a plurality of nozzles is stored in memory, the image data which is stored in the memory is subjected to an interpolation process corresponding to a faulty nozzle of a print head, the image data which is subjected to the interpolation process is subjected to a rotation process and the image data which defines the ink amount to be ejected and corresponds to each of the plurality of nozzles to be stored in the memory so as to be in a read-out order of the memory when the print head is positioned at a certain point in relation to the print medium, and the image data which is subjected to the rotation process is read out and output as the print data.