One embodiment provides a sealing apparatus of a reaction tube so as to stably support the lower portion of the reaction tube even if reaction tube is elastic in response to temperature changes in response to the change in length of the reaction tube by improving the structure so that the supporting structure is variable of the present invention that, the sealing device of the reaction tube in accordance with an aspect of the present invention, the lower cover for sealing the lower reaction tube is vertically installed on one side of the heating furnace; The lower cover on one side is connected to the lower cover is pressure-connected to the link unit in which a plurality of link members are connected to the support to close to the reaction tube; And being rotatably mounted to a side of the heating, is connected to the other side of the link unit connected to the pressure-applied rotational drive to provide a rotational force is connected to the pressing unit to press the lower cover; and a.