A method of manufacturing a titanium alloy with high strength and high formability includes preparing a material and equipment for manufacturing a titanium alloy, manufacturing a titanium alloy having a lamellar structure (martensite structure) by cooling the prepared material with water after performing heat treatment at the beta transformation temperature or more, and rolling that makes ultrafine grains by finishing forming of the titanium alloy at a plastic instability temperature by gradually decreasing the forming temperature in accordance with an increase of a strain after starting the forming at the plastic instability temperature of more, under a condition of a low strain in which the strain is 2.5 or less, after the manufacturing of a titanium alloy having a lamellar structure.