A method of separating an organic solvent, the method comprising: independently performing a process of introducing a first mixed solution containing an organic solvent and high boiling point compound A, that comprises an unreacted aromatic vinyl-based monomer, a dimer of conjugated diene-based monomer, a trimer of the conjugated diene-based monomer, a dimer of an aromatic vinyl-based monomer and a trimer of the aromatic vinyl-based monomer, into a first distillation column to recover the organic solvent from a top of the column and discharge a first fraction containing an unrecovered organic solvent and the high boiling point compound A to a bottom of the column; and a process of introducing a second mixed solution containing an organic solvent and high boiling point compound, that comprises a dimer of conjugated diene-based monomer and a trimer of the conjugated diene-based monomer, into a second distillation column to recover the organic solvent from a top of the column and discharge a second fraction containing an unrecovered organic solvent and the high boiling point compound B to a bottom of the column; and introducing the first fraction and the second fraction into a third distillation column to recover an organic solvent-rich fraction from a top of the column and a high boiling point compound-rich fraction containing the high boiling point compound A and the high boiling point compound B from a bottom of the column, wherein the high boiling point compound-rich fraction comprises an unreacted aromatic vinyl-based monomer in an amount of less than 30 wt%; wherein the step is performed under a condition in which a bottom temperature and a pressure of the third distillation column are adjusted to be less than 100°C and less than 0.4 bar, respectively; wherein the first mixed solution is a residual solution in which a polymer is removed from a steam stripping process in a solution-polymerized styrene-butadiene copolymer preparation process, whereby the residual solution includes an organic solvent, a conjugated diene-based monomer, a dimer and a trimer of the conjugated diene-based monomer, an aromatic vinyl-based monomer, and a dimer and a trimer of the aromatic vinyl-based monomer, and the second mixed solution is a waste solution in which a polymer is removed from a steam stripping process in a rare earth metal catalyzed butadiene polymer preparation process, whereby the residual solution includes an organic solvent, a conjugated diene-based monomer, and a dimer and a trimer of the conjugated diene-based monomer. independently performing a process of introducing a first mixed solution containing an organic solvent and high boiling point compound A, that comprises an unreacted aromatic vinyl-based monomer, a dimer of conjugated diene-based monomer, a trimer of the conjugated diene-based monomer, a dimer of an aromatic vinyl-based monomer and a trimer of the aromatic vinyl-based monomer, into a first distillation column to recover the organic solvent from a top of the column and discharge a first fraction containing an unrecovered organic solvent and the high boiling point compound A to a bottom of the column; and a process of introducing a second mixed solution containing an organic solvent and high boiling point compound, that comprises a dimer of conjugated diene-based monomer and a trimer of the conjugated diene-based monomer, into a second distillation column to recover the organic solvent from a top of the column and discharge a second fraction containing an unrecovered organic solvent and the high boiling point compound B to a bottom of the column; and introducing the first fraction and the second fraction into a third distillation column to recover an organic solvent-rich fraction from a top of the column and a high boiling point compound-rich fraction containing the high boiling point compound A and the high boiling point compound B from a bottom of the column, wherein the high boiling point compound-rich fraction comprises an unreacted aromatic vinyl-based monomer in an amount of less than 30 wt%; wherein the step is performed under a condition in which a bottom temperature and a pressure of the third distillation column are adjusted to be less than 100°C and less than 0.4 bar, respectively; wherein the first mixed solution is a residual solution in which a polymer is removed from a steam stripping process in a solution-polymerized styrene-butadiene copolymer preparation process, whereby the residual solution includes an organic solvent, a conjugated diene-based monomer, a dimer and a trimer of the conjugated diene-based monomer, an aromatic vinyl-based monomer, and a dimer and a trimer of the aromatic vinyl-based monomer, and the second mixed solution is a waste solution in which a polymer is removed from a steam stripping process in a rare earth metal catalyzed butadiene polymer preparation process, whereby the residual solution includes an organic solvent, a conjugated diene-based monomer, and a dimer and a trimer of the conjugated diene-based monomer.