The present invention relates to a method for continuously preparing a diester-based material comprising a reaction part in which all N reaction units from a first reaction unit to an N-th reaction unit are connected to each other in serial, the method comprising a step of injecting a dicarboxylic acid and a primary alcohol, wherein the primary alcohol is dividedly injected through a pre-injection of being injected into the first reaction unit and a post-injection of being injected into one or more reaction units selected from among a second reaction unit to the N-th reaction unit, the amount of the post-injection is 5-80 wt% on the basis of the total amount of the primary alcohol to be injected into the reaction part, and N is an integer of 3-6. Compared with a conventional batch process, the present invention can reduce a reflux amount, ensure the convenience of process operation through a reduction in the amount of steam for heating a reactor, and ensure the economic feasibility of a product through energy reduction.