Method of detecting an nucleic acid and oligonucleotide probe

Provided is a method for detecting a target sequence, said method comprising: a hybridization step for contacting an oligonucleotide probe, which has a sequence hybridizable with a target sequence of a nucleic acid present in a test sample and, in the hybridizable sequence, at least one covalent bonding group crosslinkable by light irradiation with a target base in the target sequence when specifically hybridized with the target sequence, with the nucleic acid to form an authentic hybridization product; a light irradiation step for, after the hybridization step, irradiating the test sample with light and thus crosslinking between the covalent bonding group and the target sequence in the authentic hybridization product to form an authentic hybridization product having a crosslinked structure; and a denaturation step for, after the light irradiation step, imparting to the test sample denaturation conditions, which allow the maintenance of the crosslinked authentic hybridization product and the dissociation of a