PURPOSE: To prevent occurrence of crack in rollers while retaining a high hardness and wear resistance thereof by forming a coat by nickel alloy plating on the surface of a printing roller, through which printing paper is passed in contact therewith after being printed by a guide roller and common impression cylinder.

CONSTITUTION: Since a roll paper moves at high speed, it travels through guides 6b-6m and reaches a common impression cylinder 11 of a color printing rotary press unit 3, before the black ink printed on its back side by a black ink print ing rotary press unit 2 becomes dry. At this time, the guides 6b, 6e, 6i and 6k are in contact with the printing face of the roll paper P1. A nickel alloy plating coat is also formed on the guide 6c in order to effect a simultaneous two face printing by the rotary press unit 2 on the surfaces of the guide 6b located in a printing paper feeding passage immediately after the printing has been made by a blanket cylinder 9 of the rotary press unit 2. This coat is formed through plating of nickel based alloy and the metal elements useable therefor are molybdenum, tungsten, cobalt, phosphorus, boron and iron.