To provide a method for producing lithium tantalate single crystal which can be used as a material of a lithium tantalate substrate in that the effect of the reduction treatment is developed reproducibly and stably.

The method comprises providing a falling preventive member 9 for preventing fragments of a zirconia refractory material 2 from mixing into a raw material melt 8, wherein the member 9 is composed of a plate of a metal having a high melting point selected from Pt, Ir, Mo and W, at least on the surface facing to the raw material melt 8 of the zirconia refractory material 2 arranged on the upper side of a crucible, in a method for producing lithium tantalate single crystal by the Czochralski method using an electric furnace of a refractory material structure in which a zirconia refractory material 2 is arranged on the perimeter and the upper side of the crucible 1 in which the raw material melt 8 is held.