PURPOSE: To make the variance of molten metal level smaller when a molten metal is supplied to a triangle ladle up to the target level with tilting a stationary ladle.

CONSTITUTION: A molten metal is supplied in a triangle ladle 1 by tilting operation of a stationary ladle 2. The supply of a molten metal 3 from the high speed tilting stationary ladle 2 to the triangle ladle 1 is detected by a phototube 7, switching the stationary ladle 2 to low speed tilting operation. The supply of the molten metal 3 up to the prescribed level in the triangle ladle 1 by low speed tilting operation is detected by a camera 4 for image processing, switching the stationary ladle to tilting operation for returning. Because the camera 4 for image processing is capable of setting the focus area to any shape and size to be hardly affected by wave, the variance of molten metal supplied is reduced.