When cutting titanium alloy, the temperature of a cutting tool edge is easy to rise and the tool edge is tend to be worn away quickly because the titanium alloy has the characteristics of low thermal conductivity and high chemical activity. Therefore, it is difficult to achieve a balance between the productivity and the tool life in cutting the titanium alloy, namely, low-speed cutting must be carried out at present. To examine the possibility of the improvement in the cutting efficiency, a PCD (polycrystalline diamond) tool having high thermal conductivity was adopted to the cutting of titanium alloy and its cutting performance was investigated. The PCD tool was found to have excellent flank wear resistance compared with conventional cemented carbide tools. It was also revealed that unprecedented high speed cutting become possible by use of PCD tool with an application of high pressure coolant.