A printing machine includes a printing unit which performs printing while transferring a sheet at a printing transfer speed, a circulation transfer unit which receives the sheet after simplex printing and transfers the sheet by reversing the sheet upside down, during duplex printing; and a paper refeed unit which refeeds, to the printing unit, the sheet transferred by the circulation transfer unit after simplex printing, wherein the circulation transfer unit includes a reversing unit which receives the sheet at the printing transfer speed, reverses the sheet upside down by switching back the sheet and accelerates the sheet up to a circulation transfer speed which is higher than the printing transfer speed when sheet transfer is restarted after temporal stop in the switching back, and a horizontal transfer unit which transfers the sheet switched back by the reversing unit, at the circulation transfer speed.