To provide a rotary tube and a rotary tube furnace for producing activated carbon and to provide an appropriate apparatus for producing the activated carbon particularly.

The rotary tube (1) that is particularly for the rotary drum furnace for the production of activated carbon has a plurality of mixing elements (3). The mixing elements (3) are arranged inside the rotary tube (1) to circulate or mix a charged raw material. Particularly in the mixing elements each having a circulating or rotary plate type shape, the rotary tube (1) has opening parts (5) for respectively receiving fixing parts (6) of the mixing elements and the fixing parts (6) are welded to the outside of the rotary tube (1).