A copolycarbonate composition comprising: i) a copolycarbonate comprising an aromatic polycarbonate-based first repeating unit; and one or more aromatic polycarbonate-based second repeating units having siloxane bonds, or ii) the copolycarbonate and a polycarbonate, wherein the polycarbonate is distinguished from the copolycarbonate in that a polysiloxane structure is not introduced in a main chain of the polycarbonate, wherein the aromatic polycarbonate-based first repeating unit is represented by the following Chemical Formula 1-1: wherein the one or more aromatic polycarbonate-based second repeating units having siloxane bonds comprise a repeating unit represented by the following Chemical Formula 2-2 and a repeating unit represented by the following Chemical Formula 3-2: in the Chemical Formula 2-2, each of R 5 is independently hydrogen; C 1-15 alkyl unsubstituted or substituted with oxiranyl, oxiranyl-substituted C 1-10 alkoxy, or C 6-20 aryl; halogen; C 1-10 alkoxy; allyl; C 1-10 haloalkyl; or C 6-20 aryl, and n is an integer of 32 to 37, in the Chemical Formula 3-2, each of R 6 is independently hydrogen; C 1-15 alkyl unsubstituted or substituted with oxiranyl, oxiranyl-substituted C 1-10 alkoxy, or C 6-20 aryl; halogen; C 1-10 alkoxy; allyl; C 1-10 haloalkyl; or C 6-20 aryl, and m is an integer of 58 to 62, wherein the copolycarbonate composition has impact strength at room temperature of 830 to 1000 J/m as measured at 23°C in accordance with ASTM D256 (1/8 inch, Notched Izod), wherein the copolycarbonate composition satisfies the following Equation 1: 1.0682 × X + 0.51 < Y < 1.0682 × X + 1.2 in the Equation 1, X means a silicon content (wt.%) relative to the total weight of the copolycarbonate and polycarbonate, and Y means a value in which the FID intensity obtained through TD (Time-domain) FID experiment is normalized at 0.1 msec. i) a copolycarbonate comprising an aromatic polycarbonate-based first repeating unit; and one or more aromatic polycarbonate-based second repeating units having siloxane bonds, or ii) the copolycarbonate and a polycarbonate, wherein the polycarbonate is distinguished from the copolycarbonate in that a polysiloxane structure is not introduced in a main chain of the polycarbonate, wherein the aromatic polycarbonate-based first repeating unit is represented by the following Chemical Formula 1-1: wherein the one or more aromatic polycarbonate-based second repeating units having siloxane bonds comprise a repeating unit represented by the following Chemical Formula 2-2 and a repeating unit represented by the following Chemical Formula 3-2: in the Chemical Formula 2-2, each of R 5 is independently hydrogen; C 1-15 alkyl unsubstituted or substituted with oxiranyl, oxiranyl-substituted C 1-10 alkoxy, or C 6-20 aryl; halogen; C 1-10 alkoxy; allyl; C 1-10 haloalkyl; or C 6-20 aryl, and n is an integer of 32 to 37, in the Chemical Formula 3-2, each of R 6 is independently hydrogen; C 1-15 alkyl unsubstituted or substituted with oxiranyl, oxiranyl-substituted C 1-10 alkoxy, or C 6-20 aryl; halogen; C 1-10 alkoxy; allyl; C 1-10 haloalkyl; or C 6-20 aryl, and m is an integer of 58 to 62, wherein the copolycarbonate composition has impact strength at room temperature of 830 to 1000 J/m as measured at 23°C in accordance with ASTM D256 (1/8 inch, Notched Izod), wherein the copolycarbonate composition satisfies the following Equation 1: 1.0682 × X + 0.51 < Y < 1.0682 × X + 1.2 in the Equation 1, X means a silicon content (wt.%) relative to the total weight of the copolycarbonate and polycarbonate, and Y means a value in which the FID intensity obtained through TD (Time-domain) FID experiment is normalized at 0.1 msec.