1. An evaluation system for displaying analysis results of the length of a PCR amplification product of a DNA fragment containing a microsatellite, comprising: a graph display processing unit for displaying a graph of the detection signals of the PCR amplification product, in which the axes denote detection signal intensity and fragment length, respectively; a first determination processing unit for determining +A peaks derived from the detection signals of the PCR amplification product in which one adenine is added to the DNA fragment end and peaks excluding +A peaks based on the detection signals of the PCR amplification product; a second determination processing unit for determining true peaks derived from the detection signals of the PCR amplification product of the DNA fragment and stutter peaks derived from the detection signals of the PCR amplification product in which a microsatellite repetitive sequence is increased or decreased by one unit or more based on the detection signals of the PCR amplification product; a determination result display processing unit for displaying the results of the determination of +A peaks and peaks excluding +A peaks, the results of the determination of true peaks and stutter peaks, together with the graph; and a database that stores analysis results of the length of the PCR amplification product of the DNA fragment containing the microsatellite obtained from each of a plurality of individuals; wherein determination results obtained in the first and second determination processing units are evaluated based on at least one of the following criteria: (1) whether or not the height ratio of a true peak and a stutter peak subjected to determination differs significantly from the same ratios derived from a plurality of individuals stored in the database; (2) whether or not the height ratio of a true peak and a +A peak subjected to determination differs significantly from the same ratios derived from a plurality of individuals stored in the database; and (3) whether or not fragment lengths associated with true peaks, stutter peaks, and +A peaks subjected to determination differ significantly from those obtained from a plurality of individuals stored in the database.