A first liquid raw material and a second liquid raw material are reacted with each other by a reactor of a reaction device, so that a reaction product is produced. The reaction product is analyzed by an analyzer. In the controller, the reference value is acquired by the reference value acquirer from the chromatogram obtained from the result of the analysis by the analyzer. An upper limit value and a lower limit value with respect to the reference value are set by an allowable range setter. At least one of a residence time of the first liquid raw material, a residence time of the second liquid raw material, a reaction temperature, and a reaction pressure in the reactor is dynamically changed as a control target by a reaction controller such that the reference value falls between the upper limit value and the lower limit value.