To provide a method for squeezing residual steel quantity in a tundish with which the residual steel quantity in the tundish is grasped more precisely than before and flowing-out of slag into a mold can be restrained.

When the molten steel covered with the slag and held in the tundish, is continuously cast through a nozzle provided with a gate for opening/ closing by sliding, a sensor freely ascended/descended for detecting the surface height of the molten steel in the lowered slag and molten steel, is arranged. When the distance from the bottom surface of the tundish to the molten steel surface calculated on the basis of the difference between the detected value and the position of the sensor reaches a predetermined threshold value, the above gate is closed.