To efficiently execute the cooling of Al dross and the recovery of Al metal by continuously supplying the Al dross into a double structural rotary drum, indirectly water-cooling in the drum under Ar gas atmosphere and continuously discharging the cooled material.

The Al dross is continuously supplied into a rotary drum 11. Cooling water is spread onto the outer peripheral surface of an inner cylinder 21 from nozzles 28 through a cooling water supplying pipe 27 arranged at a hollow part between the inner cylinder 21 and an outer cylinder 22 in the rotary drum 11, and the spread cooling water is drained from a drainage hole 29 arranged at the outer cylinder 22. Gaseous Ar is supplied into the inner cylinder 21 from an opening hole 31 arranged at the inner cylinder 21 and exhausted from an exhausting hole 15 at a supplying chamber 12. In such a way, the Al dross continuously supplied into the inner cylinder 21 is indirectly water-cooled under Ar gas atmosphere while feeding it from the one end part to the other end part in the inner cylinder 21. When the inner cylinder 21 is rotated and one of an opening part 32 arranged in the extension part is communicated with an opening part 34 in a cover 33, the cooled material is dropped by gravity into a discharging chamber 35 and finally, discharged by opening a discharging door 37.