PURPOSE: To miniaturize a printing device and make it possible to selectively use a printing function alone or a combined function of printing and folding by installing a folder device which can be selectively changed over to operation or non-operation between the printing mechanism and the sheet delivery mechanism of a sheet-printer.

CONSTITUTION: A sheet of paper to be printed is fed from an intermediate cylinder 1 to a back rubber cylinder 2 which gives the last color impression and its both sides are printed by a front rubber cylinder 3, a front plate cylinder 4 and a back plate cylinder 5 at the contact point of the front rubber cylinder 3, and the printed paper is sent out from another intermediate cylinder 6. Then, the printed paper discharged from the printing mechanism is folded by a folding cylinder 10 and then is caused to wrap around a gripper cylinder 12 and rotates and is released from the cylinder at a proper position, and it is moved horizontally, being caught between belts 14, 15 and it is folded by a knife folding device 13 at a position near the end of the belts. When the printed paper need not be folded, the folding cylinder 10 is changed-over to nonoperating position, and the printed paper is gripped by a chain gripper 84 and discharged from a delivery cylinder 8.