PURPOSE: To obtain a desired picture without any fault in the picture even when an abnormal printing element is generated.

CONSTITUTION: A predetermined pattern is printed on a printing material 9 exclusive for monitoring by a printing head 7 while the pattern is read by a reading device 11 to detect an abnormal printing element. A picture data, to be added to the abnormal printing element, is moved based on the result of the detection to superpose it oh the picture data of another printing element and complete the printing whereby a picture having no defect can be obtained.