A printing system comprising: a controller that generates image data and controls printing; a first paper supplier that unwinds and supplies a printing medium wound around a winding shaft; a first image-forming unit that forms a first image based on image data, on the printing medium unwound and supplied by the first paper supplier; a winder that winds the printing medium on which the first image-forming unit formed the first image around a winding shaft in order from a beginning edge to a ending edge of the printing medium; a second paper supplier that unwinds and supplies the printing medium the winder wound around the winding shaft, in order from the ending edge to the beginning edge of the printing medium; and a second image-forming unit that forms a second image based on image data in which top and bottom have been reversed and left and right have been reversed in the area where the first image was formed on the printing medium unwound and supplied by the second paper supplier.