An image processing unit comprises a memory for storing original image data and a print start time therefor, and a reserve print function of reading the original image data from the memory and printing the same at the print start time. The image processing unit further has a monitor for monitoring consumed times for an interruption copy, paper supply and the like, an operator for inputting print data and a desired print end time, a computing element for operating a required time for a print operation on the basis of the print data, and a setter for setting a print start time for each original on the basis of the operating situation of the image processing unit and the required and desired end times for each original for avoiding overlapping of print operations for respective originals.