β-type titanium alloy exhibiting super-elasticity and super-plasticity was developed. This alloy has high tensile stress and low young's modulus too. The excellent characteristics of this alloy indicate its likely application in the field of dental implant. However, the characteristics of this alloy is lost by severe heat environment and external force. In this study, the effect of cutting temperature and cutting force on the affected layer was investigated by milling with small ball end mill tool in order to decrease the affected layer by cutting process. The thickness of affected layer indicated a tendency to increase with the cutting speed. And at the cutting speed of 16.0m/s, the thickness of the affected layer exceeded 2.5μm because of increasing of cutting temperature. On the other hand, the thickness of affected layer was 0.7μm at the condition of the environment of high cutting force. Thus, the affected layer influenced by cutting temperature.