PURPOSE: To prevent paper tearing without bringing about excessive trouble by spraying an α-olefin solvent having a specific number of carbon atoms on the ink films on a blanket cylinder at the start of printing.

CONSTITUTION: Printing ink is transferred to ink fountain rollers 7, 7', ink doctors 8, 8', ink distributing rollers 9, 9', ink distributors 10, 10', ink distributing rollers 11, 11', ink distributors 12, 12', form rollers 13, 13', plate cylinders 14, 14' having plates attached thereto and blanket cylinders 15, 15' from ink fountains 6, 6'. In such a state that paper 16 is passed through the gap between the blanket cylinders 15, 15', the 4-30C α-olefin solvent (octene-1) contained in manual sprayers 17, 17' is sprayed on the ink films on the blanket cylinders 15, 15' for 5sec. Subsepuently, both surfaces of the paper 16 are brought into contact with the blanket cylinders 15, 15' to start printing. By this constitution, printing can be well performed without generating paper tearing.