PURPOSE: To prevent connection of a gate side shell and a twin mold roller side shell by moving back and forth heat-resistant bar-shaped bodies disposed near the tangent between the inside circumferential surface of gates and the outside circumferential surface of the twin mold rollers along the axial central direction thereof.

CONSTITUTION: A continuous casting plant produces a light-gauge steel sheet 8 by pouring a molten metal 6 from a tundish nozzle 5 into gates 2 provided above twin mold rollers 1 and consisting of a heat insulating material and drawing a shell 7 formed on the rollers 1 rotating in the arrow A direction toward the arrow B direction by means of guide rollers 3 and pinch rollers 4. Heat-resistant bar-shaped bodies 11 are disposed near the tangent between the inside circumferential surface of said gates 2 and the outside circumferential surface of the rollers 1 with the above-mentioned continuous casting plant and the bodies 11 are moved back and forth along the axial center direction thereof within a specified range. The connection between the gate side shell 9 and the twin mold roller side shell 7 is thus prevented or the connection is interrupted to prevent the generation of the deformation and breakout of the sheet 8.