A titanium alloy having ultrahigh strength and ultralow elastic modulus, and showing linear elastic deformation behavior is disclosed. The titanium alloy (Ti-20Nb-5Zr-1Fe-O) of the present invention consists of titanium, niobium, zirconium, iron and oxygen. More specifically, the amount of niobium is 18 to 22 at. %, the amount of zirconium is 3 to 7 at. %, the amount of iron is 0.5 to 3.0 at. %, the amount of oxygen is 0.1 to 1.0 wt. %, and the balance is titanium.