PURPOSE: To prevent a sheet from being jammed and a sheet edge from being bent even if the sheet has a curl by forming on gate clicks sheet guiding parts which guide the sheet after its carrying direction is switched.

CONSTITUTION: The sheet guiding parts 95, 96 and 97 which guide the sheet after its carrying direction is switched are provided on the gate clicks 62, 64 and 66. The carrying direction of the sheet whose one side is copied is switched by the gate clicks 62, 64 and 66, and the one-side copied sheet is guided by the sheet guiding parts 95, 96 and 97 of the gate clicks 62, 64 and 66 and surely stacked on a middle tray 37. Thus, even if the sheet has the curl, the sheet jamming and the bending of a sheet edge caused by stacking defect, etc., can be prevented.