A process for producing activated fibrous carbon comprises carbonizing and activating vegetable fibers in the presence of at least a member selected from the group consisting of ammonium salts of inorganic acids, nitric acid and boric acid and zinc chloride of about 5 to 80 parts by weight per 100 parts by weight of the vegetable fibers. The process increases remarkably a yield of activated fibrous carbon and therefore permits the supply of activated fibrous carbon at by far reduced costs as compared with the conventional process, and the resulting activated carbon shows superior adsorption capability and flexibility.