To provide a multi-color printing machine which shows quick control response; upgrades the operating efficiency of the printing machine; and achieves sufficient ink drying without wasteful consumption of materials and a device using this method.

This multi-color printing machine is equipped with a paper width controlling means which controls paper to a specified width by moistening the paper between the printing units in order to correct a lateral register deviation generated due to the changing of the width of the paper between the printing units. In addition, the paper width controlling device comprises a paper width detection means for detecting the width of the paper between the printing units of the multi-color printing machine; an arithmetic means for calculating a moistening level to the paper by comparing the detected paper width with the specified paper width; and a moistening means for moistening the paper based on the calculated moistening level. Also the paper width controlling method applied to the paper width controlling device is provided.