Surface-enhanced Raman spectroscopy (SERS) utilizes Au nanostructured surfaces where it demonstrates significant enhancement properties due to the localized surface plasmon phenomena. Here we systematically fabricated homogeneous polyvinylpyrrolidone (PVP)-stabilized Au nanostars while controlling size and apex shape with the molecular weight of PVP, so as to elucidate the correlation between structural and optical properties of nanostars. The highest sensitivity of SERS measurements realized in this study reached 26 times higher enhancement than that with conventional Au nanoparticles with a diameter of 55 nm.