There is provided a printing system which allows efficient printing at a low cost. In a printing system, unprocessed order information is arranged so as to be sequentially processed from order information which can be processed by a printer without changing paper during an unattended operation, and order information which can be processed by paper set in the printer is preferentially printed. As a result, unprocessed image information is processed in an unmanned state at the maximum. Further, before switched to an unattended operation, a paper size in which the greatest number of prints are to be prepared is selected and the selected result is notified to an operator to instruct him or her to set the paper indicated by the result in the printer, thereby allowing order information to be processed by an unattended operation at the maximum.