Disclosed is a method for manufacturing thin sheets of high-strength titanium alloys. The method includes the steps of preparing initial blanks, assembling the initial blanks into a pack within a sheath, and heating and hot rolling the pack of the initial blanks in the sheath. The method is characterized in that, in the step of preparing the initial blanks, blanks having an (.alpha.-phase grain size of not more than 2 .mu.m are produced by hot rolling a forged or die-forged slab to a predetermined value of a relative thickness h.sub.B/h.sub.F, where h.sub.B is a thickness in mm of the initial blank before said pack hot rolling and h.sub.F is a final sheet thickness in mm, and by heat treating the initial blanks followed by rapidly cooling; and in that the step of pack hot rolling is conducted in quasi-isothermal conditions in longitudinal and transverse directions, while changing a rolling direction by about 90.degree. after a predetermined total reduction in one direction is achieved. The method provides big-sized thin sheets made of high-strength titanium alloys and having homogeneous submicrocrystalline structure where an average grain size is less than 1 .mu.m. The sheets have the required mechanical properties suitable for superplastic forming (SPF) at temperatures below 800.degree. C.