It is an object of the present invention to provide a nucleic acid fragment-fixed electrode wherein a probe nucleic acid fragment is fixed on the electrode stably and in an amount-controlled manner. The present invention provides a nucleic acid fragment-fixed electrode wherein a nucleic acid fragment is fixed on the surface of a multi-component self-assembled monolayer of two or more different components which is formed on the electrode, by a covalent bond via a bifunctional linking molecule.