We have investigated the atomic-scale reaction between a Ti thin layer and highly oriented pyrolytic graphite (HOPG) mainly by scanning tunneling microscopy. A deposited Ti layer shows an epitaxial orientation structure on a HOPG substrate even in room-temperature deposition, while the bonding between Ti and HOPG is very weak. The chemical reaction between Ti and HOPG takes place, and epitaxial TiC domains on HOPG are formed for annealing at above 600 °C. The TiC domains shows a smooth surface corresponding to the TiC(111) plane after annealing at 700 °C. The formation of TiC(001) facets and significant surface roughening of not only TiC but also HOPG substrates are observed for annealing at as high as 900 °C.