High-temperature scanning tunneling microscopy (HTSTM) was applied to observe a facet structure on a Si(110) surface. The facet structures of (15, 17, 1) and (17, 15, 1) and the 16-structure were observed at 655°C. The 16-structure was formed on flat parts. It was confirmed that the 16-structure and the facet structures of (15, 17, 1) and (17, 15, 1) coexisted on the surface on which hillocks are dispersed. The hillock may be a contamination.