The screw tightening control system includes plural screw tightening apparatuses, and a control apparatus that sets a synchronization point after completion of changing tightening torques of the plural screw tightening apparatuses in a current step, and starts changing of the tightening torques of the plural screw tightening apparatuses in a next step, step by step from the synchronization point. The control apparatus causes a timing to start the changing of the tightening torque of at least one of the plural screw tightening apparatuses from the synchronization point to differ from a timing to start the changing of the tightening torque of at least another one of the plural screw tightening apparatuses. The system controls the plural screw tightening apparatuses while synchronizing them so as to avoid the inconveniences in a conventional art by a simple method.