A modified conjugated diene-based polymer comprising: a repeating unit from a conjugated diene-based monomer; a derived unit from an N-containing aromatic hydrocarbon compound; and a derived unit from an S-containing aromatic hydrocarbon compound or an S-containing heterocycle compound, and satisfying the following conditions (i) and (ii): (i) molecular weight distribution (PDI; MWD): 1.0 or more and less than 3.0; and (ii) the S content: 25 ppm or more based on a total weight of the polymer, wherein the S-containing aromatic hydrocarbon compound is a compound represented by the following Formula 2: in Formula 2, R 5 is a hydrogen atom; an alkyl group of 1 to 30 carbon atoms; an alkenyl group of 2 to 30 carbon atoms; an alkynyl group of 2 to 30 carbon atoms; a heteroalkyl group of 1 to 30 carbon atoms, a heteroalkenyl group of 2 to 30 carbon atoms; a heteroalkynyl group of 2 to 30 carbon atoms; a cycloalkyl group of 5 to 30 carbon atoms; an aryl group of 5 to 30 carbon atoms; or a heterocyclic group of 3 to 30 carbon atoms, R 6 is a single bond; or an alkylene group of 1 to 20 carbon atoms, and R 7 is an alkenyl group of 2 to 30 carbon atoms; or wherein the S-containing heterocyclic compound is a compound represented by the following Formula 3: in Formula 3, R 8 is a hydrogen atom, a substituted with a substituent X or unsubstituted alkyl group of 1 to 20 carbon atoms, a substituted with a substituent X or unsubstituted cycloalkyl group of 1 to 20 carbon atoms or a substituted with a substituent X or unsubstituted aryl group of 6 to 30 carbon atoms, R 9 is a substituted with a substituent X or unsubstituted alkylene group of 1 to 5 carbon atoms, and the substituent X is selected from the group consisting of a hydroxyl group (-OH), a halogen group, a primary amino group (-NH 2) and a secondary amino group (-NHR'), in the case where X is the secondary amino group, R' is an alkyl group of 1 to 10 carbon atoms, wherein the S content is measured as disclosed in the specification. a repeating unit from a conjugated diene-based monomer; a derived unit from an N-containing aromatic hydrocarbon compound; and a derived unit from an S-containing aromatic hydrocarbon compound or an S-containing heterocycle compound, and satisfying the following conditions (i) and (ii): (i) molecular weight distribution (PDI; MWD): 1.0 or more and less than 3.0; and (ii) the S content: 25 ppm or more based on a total weight of the polymer, (i) molecular weight distribution (PDI; MWD): 1.0 or more and less than 3.0; and (ii) the S content: 25 ppm or more based on a total weight of the polymer, wherein the S-containing aromatic hydrocarbon compound is a compound represented by the following Formula 2: in Formula 2, R 5 is a hydrogen atom; an alkyl group of 1 to 30 carbon atoms; an alkenyl group of 2 to 30 carbon atoms; an alkynyl group of 2 to 30 carbon atoms; a heteroalkyl group of 1 to 30 carbon atoms, a heteroalkenyl group of 2 to 30 carbon atoms; a heteroalkynyl group of 2 to 30 carbon atoms; a cycloalkyl group of 5 to 30 carbon atoms; an aryl group of 5 to 30 carbon atoms; or a heterocyclic group of 3 to 30 carbon atoms, R 6 is a single bond; or an alkylene group of 1 to 20 carbon atoms, and R 7 is an alkenyl group of 2 to 30 carbon atoms; or in Formula 2, R 5 is a hydrogen atom; an alkyl group of 1 to 30 carbon atoms; an alkenyl group of 2 to 30 carbon atoms; an alkynyl group of 2 to 30 carbon atoms; a heteroalkyl group of 1 to 30 carbon atoms, a heteroalkenyl group of 2 to 30 carbon atoms; a heteroalkynyl group of 2 to 30 carbon atoms; a cycloalkyl group of 5 to 30 carbon atoms; an aryl group of 5 to 30 carbon atoms; or a heterocyclic group of 3 to 30 carbon atoms, R 6 is a single bond; or an alkylene group of 1 to 20 carbon atoms, and R 7 is an alkenyl group of 2 to 30 carbon atoms; or wherein the S-containing heterocyclic compound is a compound represented by the following Formula 3: in Formula 3, R 8 is a hydrogen atom, a substituted with a substituent X or unsubstituted alkyl group of 1 to 20 carbon atoms, a substituted with a substituent X or unsubstituted cycloalkyl group of 1 to 20 carbon atoms or a substituted with a substituent X or unsubstituted aryl group of 6 to 30 carbon atoms, R 9 is a substituted with a substituent X or unsubstituted alkylene group of 1 to 5 carbon atoms, and in Formula 3, R 8 is a hydrogen atom, a substituted with a substituent X or unsubstituted alkyl group of 1 to 20 carbon atoms, a substituted with a substituent X or unsubstituted cycloalkyl group of 1 to 20 carbon atoms or a substituted with a substituent X or unsubstituted aryl group of 6 to 30 carbon atoms, R 9 is a substituted with a substituent X or unsubstituted alkylene group of 1 to 5 carbon atoms, and the substituent X is selected from the group consisting of a hydroxyl group (-OH), a halogen group, a primary amino group (-NH 2) and a secondary amino group (-NHR'), in the case where X is the secondary amino group, R' is an alkyl group of 1 to 10 carbon atoms, wherein the S content is measured as disclosed in the specification.