We studied the enhancement of excimer emission from a thin perylene dye film (10-nm thickness) by localized surface plasmon resonance (LSPR) of single gold nanoparticles (GNPs), and observed a large fluorescence enhancement factor of about 25. The absence of excitation wavelength dependence of the enhancement factor indicates that the fluorescence intensity enhancement is mainly due to an increase of the radiative emission rate by LSPR.