An activated carbon manufacturing system can efficiently heat a wood material or carbide to promote a drying process, a carbonization process and an activation process in manufacturing activated carbon, and can reduce the environmental load involved in the manufacture of activated carbon. Specifically, a drying process of a wood material is achieved by heating the wood material with saturated steam at an appropriate temperature, and an initial carbonization process of the wood material is achieved by heating the wood material with superheated steam. Therefore, the wood material can be heated with high heat transfer efficiency, so that the heat loss can be reduced, and neither a drying device nor a first carbonizing device produces a gas containing a harmful constituent in the heating processes, so that the adverse effect on the environment can be reduced.