To make it possible to prevent defects, such as cavities, pinholes, discolored parts, by removing stuck oxidized films by a cylindrical sprue disposed in a casting mold and a bamboo leaf-like device disposed in this sprue.

A wire 7 is spread in the sprue A1 of the casting mold A. This wire 7 is taken up at every pouring and the bamboo leaf-like oxidized films sticking to the wire 7 are removed. The oxidized films remaining at the sprue A1 and sticking to the wire 7 are drawn outside the sprue A1 by the taking up of the wire 7 and are scraped by a scraper 12 disposed in mid-way, by which the oxidized films are eventually cleaned every time. The causes for the defects, such as cavities, pinholes and discolored parts, in the aluminum castings, are suppressed in such a manner, by which the production capacity is greatly improved.