PURPOSE: To prevent the effect of a horizontal force and to accurately measure the level position by mounting a probe receiving the buoyancy of molten metal on an arm to support it with a slide shaft, guiding the slide shaft with a linear supporter and transmitting the buoyancy through the arm to a load cell.

CONSTITUTION: The probe 2, the arm 3, and the slide shaft 4 are integrated into one body and the slide shaft 4 moves with a linear supporter 5 as a guard, therefore, the probe 2, the arm 3, the slide shaft 4, and the weight 8 can be in a vertical direction or up and down only. Consequently, the flow of molten metal given to the probe 2 and a horizontal force F by the slag, etc., are not transmitted to the load cell 6 and the level position of the molten metal by the load cell 6 can be measured accurately.