We used a near field scanning optical microscopy (NSOM) to locally excite and detect surface plasmon (SP) in structured Au films by a consecutive process of anodic oxidation of atomic force microscope (AFM) and Au deposition process. Different types of interference patterns with the period close to a half of SP wavelength around and on the array of Au line protrusions are observed in NSOM optical transmission images, depending on the polarization direction of the incident light, which suggests a successful excitation of SP on fabricated nanostructures. The NSOM probes are believed to be somewhat coated. with Au during the scans, and these probes are found to be more efficient in exciting SP than uncoated probes. Our result shows that NSOM combined with the AFM anodic oxidation technique provides an efficient and inexpensive method to study the SP excitation on metallic nanostructures. (C) 2004 American Vacuum Society.