Vacuum or surface of the casting remains titanium slab obtained by the DC slab casting in an inert gas atmosphere, to form a re-melting and solidification layer of depth d ₁ by surface melting treatment, the said surface and rolling surface used in manufacturing the titanium material by hot rolling, a titanium slab surface melting treatment, in the thickness direction of the titanium slab, with respect to the average oxygen concentration of the base material of the titanium slab, the first region (the increment _{C 1} of the average oxygen concentration in the area) from the surface to the position of _d 1/2 or less 0.20 mass%, the average in the second region (region from the position of the _d 1/2 to the position of the _{d 1)} oxygen concentration increment _{C 2} is less _{0.05mass%, C d (= C} 1 -C 2) is not more than 0.15 mass% greater than 0, the surface melting treatment for titanium slab. This surface melting treatment for titanium slab, excellent workability in cold rolling or cold forming after hot rolling.