PURPOSE: To stably produce an ingot having fine crystal and excellent surface characteristic at the time of hot-working by forming the bottom part of a cylindrical mold for casting to a specific shape, at the time of casting into the ingot after melting a high m.p. active metal with a consumable electrode type vacuum arc melting method.

CONSTITUTION: At the time of producing a slab by melting the high m.p. active metal of an industrial pure titanium or titanium alloy, etc., with the consumable electrode type vacuum arc method, casting into the ingot and rough-casting, blooming and hot-rolling, the inner surface of the mold used at the time of casting into the ingot is formed to the cylindrical shape. Further, related to the vertical cross section passing the vertical center line in the height direction of the mold at the time of setting a two-dimensional coordinate by using Z axis for the vertical center line and R axis for the horizontal center line in the diameter direction of the mold, a side becoming Z≤0 to the orgin (R, Z)=(0, 0) is made to be the bottom side of the mold. The shape of the bottom part of the mold is made to be the shape in the three-dimensional range forming by rotating the two-dimensional range surrounded with a parabola shown in the formulas I and II while centering around the Z axis.