A gene detection method for detecting a gene having a specific sequence with high sensitivity is provided. The gene detection method comprises a double-stranded nucleic acid formation step of forming double-stranded nucleic acid by hybridizing a nucleic acid probe immobilized on an electrode and a gene sample; a step of adding an intercalator which comprises a compound having a double-stranded nucleic acid binding site Ia that is specifically intercalated into the double-stranded nucleic acid and is covalently bonded to the double-stranded nucleic acid by light irradiation, an electrochemical active site Fa having electrochemical activity, and a connecting site La for connecting the double-stranded nucleic acid binding site Ia and the electrochemical active site Fa, and has an substitution group comprising one of compounds represented by -Lb-Ib and -Lc-Fb or a combination of the both compounds, at each of the respective sites; a light irradiation step of covalently bonding the double-stranded nucleic acid and the intercalator; and a detection step of detecting the intercalator covalently bonded to the double-stranded nucleic acid by electrochemical measurement.