The electron-induced dissociation of CO2 adsorbed at the oxygen vacancy defect on the TiO2(110) surface has been investigated at the single-molecular level using scanning tunneling microscopy (STM). Electron injection from the STM tip into the adsorbed CO2 induces the dissociation of CO2. The oxygen vacancy defect is found to be healed by the oxygen atom released during the dissociation process. Statistical analysis shows that the dissociation of CO2 is one-electron process. The bias-dependent dissociation yield reveals that the threshold energy for electron-induced dissociation of CO2 is 1.4 eV above the conduction-band minimum of TiO2. The formation of a transient negative ion by the injected electron is considered to be the key process in CO2 dissociation.