Abstract: The present invention relates to a method and a kit for detecting alleles of which the specificity and sensitivity in a DNA polymerase chain reaction (PCR), which is widely used for the detection of minor alleles such as single nucleotide polymorphisms or somatic mutations, are increased. More specifically, the present invention relates to a PCR-based method and kit for single nucleotide polymorphism (SNP) genotyping and somatic mutation detection, the method and kit adding a partially or fully double-stranded oligonucleotide for increasing discrimination to a PCR solution for selective amplification of alleles, so that PCR amplification is not affected when a primer 3? terminal base is complementary (3?-matched) to a template but PCR amplification is strongly inhibited when a 3? terminal base is not complementary (3?-mismatched).