To reduce the cost of equipment and to improve quality of printing on an extremely thin paper by coping with both thin and thick sheets by one machine.

In a sheet carrying mechanism installed on a sheet-fed printing machine and holding one end of a sheet 1 with a gripper 3 and a thumb seat 4 provided on a skelton intermediate cylinder 2 and carrying it to an impression cylinder 7 provided with an air shower device 11 for printing a thick paper, an air blow sheet guide device 12 for printing a thin paper which pushes the whole region of the paper face with air A jetted from a slit opening is provided above the impression cylinder 7 is provided and a switching mechanism for switching the air blow sheet guide device 12 and the air shower device 11 in cope with the thickness of the sheet 1 is provided.