We demonstrate preparations of zinc porphyrin nanoparticles by reprecipitation method and their spectroscopic analysis by dark-field light scattering microspectroscopy. The size distribution of the prepared nanoparticles was 80-150 nm. By using dark-field illumination the nanoparticles could be observed as bright points in dark background and could be examined by their Rayleigh scattering spectra at single particle level. The spectra differed from particle to particle, which would be ascribed to their size and crystalline phase difference. Thus we have performed this single particle spectroscopic technique to remove the ambiguity about the spectroscopic information owing to distributions of particles and to improve the space selectivility. In addition, we have successfully demonstrated the detection of amine molecules in water at single particle level. These results indicate that the detection technique using the single porphyrin nanoparticles can be applied to chemical and biological sensors with nanometer scale.