The (111) surface of rutile TiO2 was prepared with argon ion sputtering and vacuum annealing at 970 K. Scanning tunneling microscope observation revealed nanometer-scale domains of (1 x 1) and (1 x 2) phases on the surface. Formic acid was dissociatively adsorbed on the surface at room temperature. The recombination and decomposition temperatures of the adsorbed formate were similar to those reported on the (110) surface. The CH-related and COO-related stretching modes probed by high-resolution electron energy loss showed two or more types of formate. The wavenumber of the vibrational modes can be interpreted with a mixture of monodentate, bidentate, and bridge form of adsorption. The number density of the formates counted in microscope images supported monodentate and bidentate forms. Sequential imaging revealed limited mobility of the formates, reflecting the wide separation of surface Ti atoms.