A polymer including a repeating unit represented by the following Chemical Formula 1, a repeating unit represented by the following Chemical Formula 2, and a repeating unit represented by the following Chemical Formula 3: in Chemical Formula 1, R 1 to R 3 are each independently hydrogen, or a C 1-10 alkyl, L 1 is a substituted or unsubstituted C 6-60 arylene; or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, L 2 is a single bond; a substituted or unsubstituted C 6-60 arylene; or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, Ar 1 is a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing one or more selected from the group consisting of N, O and S, Ar 2 and Ar 3 are each independently a substituted or unsubstituted C 1-60 alkoxy, a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing one or more selected from the group consisting of N, O and S, in Chemical Formula 2, R 4 to R 6 are each independently hydrogen, or a C 1-10 alkyl, L 3 is a single bond; a substituted or unsubstituted C 6-60 arylene; (substituted or unsubstituted C 6-60 arylene)-O-; (substituted or unsubstituted C 6-60 arylene)-O-(substituted or unsubstituted C 1-60 alkylene); or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, in Chemical Formula 3, R 7 to R 9 are each independently hydrogen, or a C 1-10 alkyl, L 4 is a single bond; a substituted or unsubstituted C 6-60 arylene; or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, Ar 4 is a substituted or unsubstituted C 3-60 cycloalkyl, a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing one or more selected from the group consisting of N, O and S, Ar 5 is hydrogen, or a substituted or unsubstituted C 6-60 aryl, n is an integer of 0 to 5, and x, y and z are molar ratios of a repeating unit of Chemical Formula 1, a repeating unit of Chemical Formula 2 and a repeating unit of Chemical Formula 3 in the polymer, respectively. R 1 to R 3 are each independently hydrogen, or a C 1-10 alkyl, L 1 is a substituted or unsubstituted C 6-60 arylene; or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, L 2 is a single bond; a substituted or unsubstituted C 6-60 arylene; or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, Ar 1 is a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing one or more selected from the group consisting of N, O and S, Ar 2 and Ar 3 are each independently a substituted or unsubstituted C 1-60 alkoxy, a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing one or more selected from the group consisting of N, O and S, R 4 to R 6 are each independently hydrogen, or a C 1-10 alkyl, L 3 is a single bond; a substituted or unsubstituted C 6-60 arylene; (substituted or unsubstituted C 6-60 arylene)-O-; (substituted or unsubstituted C 6-60 arylene)-O-(substituted or unsubstituted C 1-60 alkylene); or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, R 7 to R 9 are each independently hydrogen, or a C 1-10 alkyl, L 4 is a single bond; a substituted or unsubstituted C 6-60 arylene; or a substituted or unsubstituted C 2-60 heteroarylene containing one or more selected from the group consisting of N, O and S, Ar 4 is a substituted or unsubstituted C 3-60 cycloalkyl, a substituted or unsubstituted C 6-60 aryl, or a substituted or unsubstituted C 2-60 heteroaryl containing one or more selected from the group consisting of N, O and S, Ar 5 is hydrogen, or a substituted or unsubstituted C 6-60 aryl, n is an integer of 0 to 5, and x, y and z are molar ratios of a repeating unit of Chemical Formula 1, a repeating unit of Chemical Formula 2 and a repeating unit of Chemical Formula 3 in the polymer, respectively.