We used sum frequency generation (SFG) spectroscopy to study the desorption of hydrogen on the stepped Si(111) surface with a miscut angle of 9.5° toward the [1 _ 1 _ 2] direction in ultra-high vacuum. The terrace peak was observed at 2085 cm −1 and the vertical step mode of dihydride was observed at 2098 cm −1 for the ssp-polarization (s-polarized SFG, s-polarized visible, and p-polarized infrared light) combination. The intensity reduction of these two peaks was monitored directly as a function of time at sample temperatures of 593 K. The rate of reduction was faster for the step dihydride peak than for the terrace monohydride peak.