PURPOSE: To print clearly all sheets from the first to the last without the multi- layer transfer of ink on a printing plate, the stuffing of the engraved cavity of the plate, etc., by controlling the timing at which an ink roll is pressed on and separated from a plate cylinder.

CONSTITUTION: An ink roll 16 is constituted so that it is pressed on and separated from a plate cylinder 12 corresponding to the start and stoppage of the supply of sheets 22. The length of an circular-arc in the direction of rotation of the plate cylinder from a contact point (a) at which the plate cylinder 12 is in contact with the ink roll 16 under pressure to a printing contact point b1 positioned at a bottom dead point at which the cylinder 12 approaches and faces an impression cylinder 14 is found, and a sensor 60 is provided on the supply route 56 of the sheets 22, apart by a dimension corresponding to said length of the circular arc from the printing contact point b1. By using this sensor, a control is made so as to detect the pass of the front end part of an initial sheet to give an instruction of pressing the ink roll on the plate cylinder 12, and to detect the pass of the rear end part of the last sheet to give an instruction of separating the former from the latter.