PURPOSE: To make it possible to cast a slab without the generation of cracks even at a high casting speed by mispositioning lateral strips outward with respect to the lateral strips of a mold section within a supporting section.

CONSTITUTION: The casting mold for continuous casting of thin slabs are provided with cooled broad walls 1 and 2 and cooled narrow walls 3 adjustably disposed between these walls. The narrow walls 3 are formed of an upper section 3a and a lower section 3b. The narrow walls 3 are provided with the different lateral strips 3b" on the inner working side within the mold section and supporting section. The lateral strips 3b" are mispositioned outward with respect to the lateral strips 3a' of the mold section 3a within the lower supporting section 3b. As a result, the final sealing by a dummy head and the adjustment of the casting mold for cast products of all sizes are facilitated.