Printer

A printer having an image division printing of forming a plurality of print images on a single sheet, and a double-sided printing function of printing both sides of the sheet, comprising:

• a printing unit having a cylinder around the outer peripheral surface of which a divided plate master having a first plate image and a second plate image aligned in a length direction is wound, and a pressure member that can freely contact with and separate from the cylinder;
• a sheet supply unit that supplies sheets to the printing unit;
• a sheet discharge unit that discharges sheets that have been printed in the printing unit outside the printer;
• an auxiliary tray that temporarily stores sheets for which a print image has been formed on the front surface thereof in the printing unit;
• sheet re-supply means for re-supplying to the printing unit the sheets that have been printed on the front surface thereof and that are stored in the auxiliary tray;
• a switching member that guides sheets that have passed the printing unit to either the auxiliary tray or the sheet discharge unit;
• image size input means for inputting the length of a document image in a main scanning direction and a sub scanning direction;
• and
• sheet size detection means for detecting the size of the sheets,
• wherein when using the image division printing function, print images corresponding to the document images formed on the sheet are arranged by carrying out either one or both of a rotation through 180 degrees process and a centering process, based on the image size input by the image size input means and the detection results of the sheet size detection means.