The present invention makes it possible to print a good quality image even if ink is ejected abnormally from a nozzle. To attain this, when there is an abnormal nozzle (N) exhibiting an abnormal ink ejection state, the printing data corresponding to the abnormal nozzle (N) is added to the printing data corresponding to neighboring nozzles (N−1) and (N+1) arranged in the neighborhood of the abnormal nozzle (N). In this way, the printing data corresponding to the abnormal nozzle (N) can be compensated.