PURPOSE: To correct curling of a sheet assuredly by stretching tight a sheet between a pair of switch rollers for clamping the leading end of the sheet and a pair of discharge rollers for clamping the trailing end of the sheet and by pressing the sheet with the projecting portion of the guide plate in a sheet reversing portion.

CONSTITUTION: A copy is made on one side of a sheet by a fixing portion 3, and the sheet is reversed by a sheet reversing portion 4. After that, the sheet is again fed to the fixing portion 3 to make a copy on the other side thereof. In this case, at a roller portion 11 of the fixing portion 3, the leading end portion of the sheet 31 discharged from a pair of discharge rollers 15, 16 is first guided to upper and lower guide plates 17, 19, and clamped between a switch roller 22 and an upper switch roller 23. At this time, the trailing end portion of the sheet 31 is still clamped between the paired discharge rollers 15, 16, and the peripheral speed of the switch roller 22 is set higher than the peripheral speed of the paired discharge rollers 15, 16. In this arrangement, the sheet 31 is stretched tight and pressed by a projecting portion 18 mounted on the lower guide plate 19 to correct curling of the sheet 31.