To provide an automatically controlled slag casting device that injects the molten slag of fixed quantity to each of all treys reliably.

In a slag casting device being provided with treys 1 that are dies for receiving molten slag, a conveyer device 2 that runs connecting between the treys 1 and an injecting device 3 injecting the molten slag into treys 1 at the upper stream side position of the conveyer device 2, the slag casting device is provided with the controller that drives the conveyer device 2 intermittently so that the empty trey 1 is stopped at a slag injecting position and after the injection of fixed quantity of the slag to it, the next empty trey 1 is brought to the injecting position and a sensor 4 being arranged to the upper part of trey 1 stopping at the injecting position detects the injected quantity to the trey 1 and the controller drives the conveyer device 2 according to the confirmation signals of the injected fixed quantity from the sensor 4.