An object of the invention is to shorten the path of back-side printing, improve the job efficiency, surely correct the curl given by a fixing roller and carry out switching for the back-side printing in a simple configuration. A duplex printing apparatus is provided with a sheet tray installed in a lower portion thereof, and first guiding device installed in one side portion thereof. Second transport path is installed in an upper portion above the first transporting device installed above the sheet tray, and installed in the second transport path are developing/image transferring device, fixing device and third guiding device, in this order from below. Installed substantially in parallel to the first transport path L1 and near one side of the duplex printing apparatus is third guiding device, and installed along the third transport path are fourth guiding device, correcting device, third transporting device and fifth guiding device, in this order from above. Second transporting device and a discharge port are installed on the opposite side of the third guiding from the fourth guiding device in this order.