Abstract: A Ti—Zr type alloy manifesting excellent plastic workability at normal temperature fit for the use in general industry, allowing improvement in corrosion resistance fit for the use in medical treatment, offering improved corrosion resistance in an acidic solution, particularly a HCl solution, and having flexibility as evinced by a low Young's modulus on a par with a bone; and a medical appliance such as a guide wire to be directly inserted into a blood vessel of a human body under the X-ray fluoroscopy and a stent retained in a human body for a long time, which are made of the Ti—Zr type alloy are provided. The Ti—Zr type alloy of the present invention consists of 25 to 50% by weight of Ti, 25 to 60% by weight of Zr, 5 to 30% by weight of Nb, and 5 to 40% by weight of Ta, provided that the weight ratio of Zr to Ti be in the range of 0.5 to 1.5 and the weight ratio of Nb to Ta be in the range of 0.125 to 1.5.