The present disclosure relates to a diester-based material production unit including a reaction device in which an esterification reaction of dicarboxylic acid and a primary alcohol is performed, a column in which the gas-liquid separation of the primary alcohol and the water introduced is performed, a heat exchanger installed on a gas phase line of the column to remove heat of the gas phase line, a flash drum in which separation of a liquid phase and a gas phase is performed in the mixture stream including the primary alcohol and the water, a condenser installed on the flash drum upper line, and a layer separator in which the layer separation of a mixture of a liquefied primary alcohol and water into an organic layer and an aqueous layer is performed, wherein one or more lines through which recirculated primary alcohol from the flash drum and the layer separator flows are connected to an upper portion of the column. According to the present invention, a coolant usage amount can be reduced and a rheological problem can be eliminated since a liquid phase and a gas phase coexist in a pipe.