To provide a sheet guiding apparatus for guiding a sheet which has a simple structure and guarantees sure sheet guiding in various operation patterns in a sheet-fed printing press.

A rotatable sheet smoothing/guiding device 2 has the first room 21 provided with a suction slot 4 and communicated with a sheet smoothing gap and this room can be solved by making it connect with an air action system 5. In addition, the sheet smoothing/guiding device 2 has the second room 20 and this room is communicated with a guiding face with an air ventilation hole 6 and has an opening part 19 in the axial direction. This opening part 19 can be functionally connected with movable casing parts 18 and 18' of a sheet guiding apparatus 13 with a flow path and an air ventilation hole 6 on its guiding face and as the result, air feeding from the flow path to the room 20 is possible.