Whether a continuous sheet usable for printing on the basis of first print data and a continuous sheet usable for printing on the basis of second print data are the same or not is determined. If it is determined that they are the same, an image based on the first print data and an image based on the second print data are printed continuously on a continuous sheet. When an image based on the second print data is arranged at an end of a continuous sheet, the second print data is assigned to the beginning of print data to be printed on another continuous sheet.