We fabricated the gold nano-aperture plasmonic nano-apertures on the pyramid. The Au aperture size ranging from ~10 to ~100 nm with a various shape were fabricated on top of the pyramidal apertures by using a focused Ga ion beam milling (FIB) and transmission electron microscopy (TEM) in addition to the conventional Si microfabrication process. In this report, we investigated the optical characteristics of the fabricated plasmonic nano-apertures in the visible range, dependent upon the aperture size. The optical enhancement of the transmitted light through the nano-aperture can be obtained by not only using surface plasmon polariton (spp) interactions with incoming wav, but also, and spp- mediated inherent intraband emission of the Au surface from the backward scattering at the pyramidal apex. As the size of the nano-aperture decreases, the intensified backward diffracted beam from the nano-aperture at the pyramidal apex will lead to higher optical intensities via spp-mediated intraband emission at ~500 nm. The fabricated Au nano-aperture array platform with a nano-meter size aperture can be utilized as a single-molecule sensor.