A method for continuously purifying a reaction product of esterification, the method comprising: a step S1 of performing layer separation on an unpurified product mixture including an alcohol mixture, as an unreacted material, containing two kinds of alcohol having different numbers of carbon atoms selected from 3 to 10 carbon atoms and including ester which is a product of an esterification reaction into an organic layer fraction which is rich in ester and a water layer fraction including lower alcohol in the presence of a basic aqueous solution, which is injected through a neutralization agent injection port, in a neutralizer having a partition wall structure; a step S2 of injecting the organic layer fraction into a distiller to remove an alcohol-rich stream from an upper portion of the distiller and to discharge an ester-rich stream from a lower portion thereof; and a step S3 of injecting the ester-rich stream into a product purifier to separate an ester fraction from a lower portion of the product purifier and to separate an alcohol fraction from an upper portion thereof, wherein the ester is one or more selected from the group consisting of terephthalate, isophthalate, phthalate, cyclohexane 1,2-diester, cyclohexane 1,3-diester, cyclohexane 1,4-diester, citrate, trimellitate, cyclohexane tricarboxylate-based compound, benzene tetracarboxylate-based compound, furan tetracarboxylate-based compound, cyclohexane tetracarboxylate-based compound and tetrahydrofuran tetracarboxylate-based compound, and wherein the neutralizer includes an inlet into which an unpurified product mixture containing a mixture of two kinds of alcohols having different esters and different numbers of carbon atoms is injected, a neutralization agent injection port through which a basic aqueous solution is injected as a neutralization agent, an inner space in which neutralization and water separation are performed, a first discharge port from which an organic layer fraction is discharged, and a second discharge port from which a water layer fraction is discharged, and the neutralization agent injection port is provided on the side of the neutralization space. a step S1 of performing layer separation on an unpurified product mixture including an alcohol mixture, as an unreacted material, containing two kinds of alcohol having different numbers of carbon atoms selected from 3 to 10 carbon atoms and including ester which is a product of an esterification reaction into an organic layer fraction which is rich in ester and a water layer fraction including lower alcohol in the presence of a basic aqueous solution, which is injected through a neutralization agent injection port, in a neutralizer having a partition wall structure; a step S2 of injecting the organic layer fraction into a distiller to remove an alcohol-rich stream from an upper portion of the distiller and to discharge an ester-rich stream from a lower portion thereof; and a step S3 of injecting the ester-rich stream into a product purifier to separate an ester fraction from a lower portion of the product purifier and to separate an alcohol fraction from an upper portion thereof, wherein the ester is one or more selected from the group consisting of terephthalate, isophthalate, phthalate, cyclohexane 1,2-diester, cyclohexane 1,3-diester, cyclohexane 1,4-diester, citrate, trimellitate, cyclohexane tricarboxylate-based compound, benzene tetracarboxylate-based compound, furan tetracarboxylate-based compound, cyclohexane tetracarboxylate-based compound and tetrahydrofuran tetracarboxylate-based compound, and wherein the neutralizer includes an inlet into which an unpurified product mixture containing a mixture of two kinds of alcohols having different esters and different numbers of carbon atoms is injected, a neutralization agent injection port through which a basic aqueous solution is injected as a neutralization agent, an inner space in which neutralization and water separation are performed, a first discharge port from which an organic layer fraction is discharged, and a second discharge port from which a water layer fraction is discharged, and the neutralization agent injection port is provided on the side of the neutralization space.