To solve the problem wherein discrimination between a peak caused by a noise and a peak caused by DNA is difficult, when performing SNPs determination from a result acquired by performing electrophoresis.

Data measured in a plurality of times during electrophoresis are binarized, and a peak appearing on the same place is recognized as a noise. A position to which a peak caused by DNA is moved by the electrophoresis is assumed, and when each peak position of scanning data of optional one cycle and scanning data of the next one cycle are not in a range of a prescribed moving distance, the peak position is determined to be a noise. Hereby, noises can be reduced, and accurate SNPs determination becomes possible.