Provided is a genotyping method. The genotyping method includes using a DNA chip on which just an optimal probe set is immobilized, the optimal probe sets composed of a discriminating probe which perfectly matches a mutant type gene or a wild type gene for each of at least one identified mutation site in each of at least one amplicon contained in a sample and an amplicon probe having a sequence which perfectly matches a region excluding a nucleotide sequence at a mutation site in each amplicon and is absent from the other amplicons, in order to identify which one of a wild type gene and a mutant type gene is present in each mutation site. In this genotyping method, the number of probes used can be reduced and reliability of genotyping results can be increased.