The c(4 x 2)-CO/Ni(111) surface under pulsed near-infrared irradiation is examined by time-resolved sum-frequency generation (SFG) spectroscopy. At a surface coverage of 0.5, the surface is confirmed to consist almost exclusively of hollow CO molecules, as evidenced by a sole SFG peak at 1904 cm(-1). Under pulsed irradiation, this peak weakened, followed by the emergence of a new peak attributable to atop CO. This represents a direct observation of site-hopping of adsorbed CO. The hopping phenomenon was found to be entirely transient, with the surface returning to the pre-excited state within a few hundred picoseconds without desorption. The dynamics of the process are also discussed.