Titanium or titanium alloy, which is generally easy to adhere, is not suitable for tool materials because of its poor wear resistance. However, the adhesion reaction of the β-type titanium alloy can vary depending on its friction counterpart, and it was found that the adhesion reaction of the β-type titanium alloy was lower in the artificial cortical bone and the cow bone than in the SUS 304. A drill made of β-type titanium alloy, whose surface was hardened by an oxygen solid solution diffusion treatment and an age hardening treatment, exhibited wear resistance comparable to that of the commercially available SUS420J2 drill. If the β-type titanium alloy is subjected to the oxygen solid solution diffusion as well as the age hardening treatments, there is a possibility that the β-type titanium alloy can be used as a medical tool material.