1. A method for manufacturing a fuel injection control system controlling an injection of fuel in an internal combustion engine with a fuel injection valve, the method comprising steps of: preparing for manufacturing including: a first step wherein a plurality of measurement points are set in a map based on at least one of a pressure of the fuel supplied to the fuel injection valve and an injection period of the fuel in the fuel injection valve, the map being defined by an injection amount and the injection period in which the pressure is taken as a parameter, and one or more preparing fuel injection valves are subjected to measurement of variability in injection characteristics thereof at every adjustment point; a second step wherein the plurality of adjustment points are classified into two groups consisting of one group composed by actual-measuring points and the other group composed by predicting points and, using the measured variability in the injection characteristics, a predicting expression predicting variability in the injection characteristics at the predicting points from variability in the injection characteristics at the actual-measuring points is produced and memorized; a third step wherein, by using the measured variability in the injection characteristics, a first relationship among the variability in the injection characteristics at the actual-measuring points is defined and memorized; measuring variability in injection characteristics of each of manufactured fuel injection valves at the actual-measuring points; and adjusting a manipulated variable to each of the manufactured fuel injection valves by using measurements of the variability measured in the measured step, a second relationship among the measurements of the variability measured in the measured step, the first relationship among the variability in the injection characteristics memorized in the third step, and the predicting expression memorized in the second step.