The adsorption structure of nitric oxide (NO) on Pt(111) was studied at 10 and 70 K by scanning tunneling microscopy (STM). The island growth modes at both temperatures are similar except for the domain size of the 2X2 structure. In these low temperature region, two phases can coexist at medium coverages. These phases are assigned to the two NO species occurring at different stretching-vibrational frequencies observed in the previous vibrational spectroscopic studies. The relative location of two different species observed by STM and its stretching-vibrational frequencies suggests that the adsorption sites of NO on the Pt(111) surface at low and high coverages correspond to the hollow and the on-top sites, respectively.