PURPOSE: To provide a clutch control system in a printing machine capable of closing unit clutches in a short time so as to shorten a starting time for printing operation.

CONSTITUTION: At first, unit clutches 1b, 2b, 3b, 4b of print units 1-4 are closed with closing of a main power source. Thereafter, conformity or non-conformity in phases at power side and unit side is compared based on phase information of an encoder 11 for detecting a phase of a line shaft 6 and encoders 1c-4c for detecting phases of plate cylinders 1a-4a, so that only the unit clutches 1b-4b of the print units 1-4 which are not conformed are selectively conformed to the phase at the power side.