Provided is a production apparatus (100) for continuously producing aligned carbon nanotube aggregates on a substrate supporting a catalyst while continuously transferring the substrate. The production apparatus (100) includes gas mixing prevention means (12, 13) for preventing gas present outside a growth furnace (3a) from flowing into the growth furnace (3a). The gas mixing prevention means (12, 13) includes a seal gas ejection section (12b, 13b) so that the seal gas does not flow into the growth furnace through the openings of the growth furnace. The production apparatus prevents the outside air from flowing into the production apparatus, uniformly controls, within a range suitable to production of CNTs, a concentration distribution(s) and a flow rate distribution(s) of a raw material gas and/or a catalyst activation material on the substrate, and does not disturb gas flow as much as possible in the growth furnace.