PURPOSE: To produce small lot without shrinkage and segregation by making bottom plate of a mold shiftable and heating molten metal and slab.

CONSTITUTION: The front face plate 11, back face plate 12 and both side plates 13, 14 in the mold are formed with a material having m.p. higher than that of the slab, and both side plates 13, 14 are arranged as adjustable to position of right and left directions according to the width of the slab to be obtained. The bottom plate 15 is arranged as adjustable to position of vertical direction according to the length of the slab to be obtained. Further, at the prescribed position surrounding outsides of both side plates 13, 14 and the front face and back face plates 11, 12, heating sources 18 for heating the mold and molten metal are set. By turning the heating sources 18 to 'ON', the mold is heated and the molten metal is successively poured into cavity part 16 of the mold. By turning the heating sources 18 to 'OFF' from the lower part in order, the unidirectional solidification is executed.