To have a press cylinder and ink rollers of an ink supply device positioned symmetrically relative to a form cylinder, and reduce their press load relative to the form cylinder by locating the press cylinder and the ink rollers of the ink supply device at a substantially opposite position of 180° about the form cylinder.

An ink supply device 9 is installed at a substantially opposite position of 180° about a form cylinder 1 in the proximity with each other, and solenoids 20 are driven so that ink rollers are pressed against against a printing plate 3 wound there around independently every color, and the solenoids 20 are arranged on the outer periphery of the form cylinder 1 for implementing selection operation on the basis of an output signal from a sensor 21 adapted to detect the position of the printing plate 3. Furthermore, the ink supply device 9 operates to detect the position of rotating form cylinder l by every color sensor 21 set near the outer periphery of the form cylinder 1, thereby making the solenoids 20 'ON' at the timing after a lapse of predetermined time as the printing plate 3 having the purpose color passes therethrough for permitting the ink roller to be pressed against the printing plate 3, and performing the start timing In a nonimage part of the printing plate 3.