A near-field light detecting apparatus providing a high spatial resolution comprises
a near-field light sensor for converting near-field light from the surface of a
sample into an electric signal, and a voltage source for applying a predetermined
voltage to the near-field light sensor through wires. The near-field light sensor
comprises a nanotube which has an insulating property in a predetermined area.
Electronic excitation is induced by the near-field light in two areas separated
by the insulating area to convert the near-field light into the electric signal.