The disclosure of this Description includes: a step of preparing a solid-phase body provided with a detection probe having a predetermined nucleotide sequence; a step of preparing a signaling target nucleic acid having a signal generating part for detecting the target nucleic acid; a step of bringing the signaling target nucleic acid, the detection probe, and an oligonucleotide being a mediator having a first site that hybridizes specifically with the target nucleic acid and a second site (preferably 20 to 50 nucleotides or more preferably 20 to 25 nucleotides in length) that hybridizes specifically with a part having the predetermined nucleotide sequence of the detection probe into contact with one another so that a hybridization product of these components can be formed; and a step of obtaining data based on the signal generating part of the signaling target nucleic acid on the solid-phase body.