In a method of recycling iron and steel industry waste by processing the waste as an object substance by the use of a rotary kiln, the object substance is changed into a valuable material while the object substance travels within the rotary kiln from an upstream side to a downstream side. The object substance is heated on the upstream side of the rotary kiln within a reducing atmosphere to be reduced and molten into a reduced and molten product. The reduced and molten product is quickly sent to the downstream side without being adhered to an internal wall of the rotary kiln. The valuable material is extracted from the reduced and molten product which may be directly discharged out of the rotary kiln or which may be discharged after the reduced and molten product is once kept in a basin formed in the vicinity of the downstream side of the rotary kiln.