Poster printing and double-sided printing are realized concurrently by controlling an order of outputting pages for a divided image. A printer prints two consecutive pages of print data on both sides of a sheet of paper, and a host computer generates print data such that each page of print data is enlarged and divided and resultant data is printed on a plurality of media. A first page of print data is divided into a predetermined number of pieces in accordance with the number of sheets of print paper, and a second page of print data is divided in the same manner. Respective pieces of print data for the first and second pages are selected from the pieces of print data. Then, the selected pieces of print data for the first and second pages are printed on front and back sides, respectively, of a medium.