A mechanism for optimizing insulin infusion rate of a CSII pump for each patient. A continuous subcutaneous insulin infusion therapy uses a continuous subcutaneous insulin pump, which includes: determining a circadian variation curve representing sympathetic nerve activity and that represents parasympathetic nerve activity of a target patient; acquiring an inflection point of each of the circadian variation curves representing the two types of nerve activity; detecting a time that corresponds to the inflection point; and employing the time as a point at which the insulin infusion rate of the continuous subcutaneous insulin infusion pump is changed.