Localized laser-induced heating of an individual Au nano-dimer was quantitatively evaluated by measuring the surface-enhanced Raman scattering (SERS) from an isolated single-walled carbon nanotube (SWNT) supported above the nano-gap between the two metal centres of the dimer. The SERS measurement showed an apparent wavenumber shift in the G-band of the Raman spectra with an increase in the power of the illuminated laser light, indicating the laser-induced local thermal elevation of the Au nano-dimer. In addition, it was found that the effect of the laser illumination on the thermal elevation in air was larger than that in aqueous solution, indicating that the localized laser-heating effect is strongly influenced by the surrounding environment. The present technique provides a measure of the highly localized heating effect of plasmonic metal nanostructures under photo-illumination.