PURPOSE: To improve quality of a product ingot by removing the floating slag on the surface of molten metal after a moving scraping plate and fixed scraping plate are joined and the slag floating on the surface of molten metal is scraped by both tip parts and the slag is squeezed by mutually turning motion of both scraping plates so as to reduce a range not to scrape as less as possible.

CONSTITUTION: A moving scraping plate 29 is traveled to the side of a fixed scraping plate at the speed higher than traveling of a mold 2 by actuation of a cylinder 32, during this travel the slag floating on the surface of molten metal, which is cast in the mold 2, is scraped/gathered, when the tip part of moving scraping plate 29 is joined to the fixed scraping plate 20 in wedge shape, the slag is turned to be squeezed by both scraping plates 20, 29. Successively, the moving scraping plate 29 is traveled further, a push bolt 31 presses a receiving part 26 and then an arm 36 at moving side is lifted/turned through joined both scraping plates 20, 29, the slag scraped such as picking up slag is subjected to squeezing and molten metal is removed.