The present invention relates to a nucleic acid analysis device for analysis of nucleic acid in a sample through fluorometry, in which a localized surface plasmon is generated by light irradiation, and in which a nucleic acid probe or a nucleic acid synthase for the analysis of the nucleic acid in the sample is disposed in a region of generation of the surface plasmon. The present invention allows the fluorescence intensifying effect of the surface plasmon to be produced efficiently and also enables the immobilization of a DNA probe or the nucleic acid synthase in a region on which the fluorescence intensifying effect is exerted, thus making it possible to carry out a measurement on the base elongation reaction without having to remove the unreacted substrate with the fluorescent molecule.