Excitation light from a light source is caused to enter a finely apertured thin metal film, having fine apertures with diameters less than or equal to the wavelength of the excitation light, formed on a surface of a substrate different from a light incident surface thereof, through the substrate, to cause near field light to be generated at the fine apertures. Fluorescent labels included in a sample liquid supplied to contact the thin metal film are caused to emit light by the near field light and by surface plasmon which are induced in the finely apertured thin metal film by the near field light. Fluorescence emitted by the fluorescent labels is detected with a detector. Fluorescent particles having a plurality of fluorescent pigments enveloped in a transmitting material that transmits both the excitation light and the fluorescence are employed as the fluorescent labels.
