The brittle fracture surfaces of titanium aluminide were investigated by the scanning tunneling microscope in the range of nanometers. The results showed that there were some river marks and/or fan patterns, ditches, dimples, and cleavage steps on the cleavage fracture surfaces. This was similar to that observed by the scanning electron microscope. The height and width of the cleavage step and the dimple size were in nanometer or quasiatomic scale.