A method to fabricate metal nanowire gratings and dotted structures on substrates by using femtosecond laser is proposed and experimentally demonstrated. By irradiating femtosecond laser pulses to a platinum thin film deposited on a fused silica substrate, platinum nanowire gratings, which periodicities were comparable to or less than half the laser wavelength, were fabricated. The structures were experimentally analyzed with scanning electron microscopy (SEM), cross sectional imaging with focused ion beam (FIB), and atomic force microscopy (AFM). Moreover, dotted structures were formed in a self-organized manner by changing the number of pulses. The method presented has potential to be used as a simple and high-throughput process for fabrication of metal nanostructures for optical, electrical, and biomedical devices.