The invention relates to the technical field of environment-friendly equipment, and particularly relates to a reaction furnace for producing active carbon. A carbonization-activation bilateral reaction furnace for producing active carbon by biomass comprises a reaction chamber, and also comprises a gas conveying pipe I, a gas conveying pipe II, a conveying pipe group, a support frame and a screen mesh, wherein the upper and lower surfaces of the reaction chamber are provided with the support frame; the upper surface of the support frame is provided with the screen; the screen is provided with sieve meshes; one end of the gas conveying pipe I is arranged on the upper side of the reaction chamber; one end of the gas conveying pipe II is arranged on the lower side of the reaction chamber; two sides of the reaction chamber are respectively provided with purification chambers. With the gas conveying pipes respectively arranged at the upper and the lower parts of the reaction furnace, bilateral reaction of biomass is realized; after primary reaction is ended, reaction gas reacts again in negative direction, so that the reaction efficiency is improved; the purification chambers arranged at the two ends of the reaction chambers achieve that reaction and purification inside the furnace are completed together; the reaction gas can be directly used after being output from the reaction furnace, reprocessing is not needed, and a subsequent processing step of reaction gas recycling is simplified.