A polycarbonate-based resin composition, comprising a blend of: a polycarbonate-based resin comprising 10 mass% to 100 mass% of a polycarbonate-polyorganosiloxane copolymer (A-1) comprising, in a main chain thereof, a repeating unit represented by the general formula and a repeating unit represented by the general formula, wherein n=10 to 500, the copolymer having a content of the repeating unit represented by the general formula of from 1.0 mass% to 10.0 mass%, and 0 mass% to 90 mass% of a polycarbonate (A-2) except the copolymer (A-1); and an additive comprising a UV absorber, wherein a content of sodium in the polycarbonate-based resin composition is 0.5 ppm or less, wherein the sodium content is determined by calculation from the remaining amount of sodium determined by inductively coupled plasma spectrometry and the amount of each component blended into the composition: wherein: R 1 and R 2 each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, X represents a single bond, an alkylene group having 1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, a cycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a fluorenediyl group, an arylalkylene group having 7 to 15 carbon atoms, an arylalkylidene group having 7 to 15 carbon atoms, -S-, -SO-, -SO 2 -, -O-, or -CO-, and a and b each independently represent an integer of from 0 to 4; and R 3 and R 4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and n represents an average number of repetitions. a polycarbonate-based resin comprising 10 mass% to 100 mass% of a polycarbonate-polyorganosiloxane copolymer (A-1) comprising, in a main chain thereof, a repeating unit represented by the general formula and a repeating unit represented by the general formula, wherein n=10 to 500, the copolymer having a content of the repeating unit represented by the general formula of from 1.0 mass% to 10.0 mass%, and 0 mass% to 90 mass% of a polycarbonate (A-2) except the copolymer (A-1); and 10 mass% to 100 mass% of a polycarbonate-polyorganosiloxane copolymer (A-1) comprising, in a main chain thereof, a repeating unit represented by the general formula and a repeating unit represented by the general formula, wherein n=10 to 500, the copolymer having a content of the repeating unit represented by the general formula of from 1.0 mass% to 10.0 mass%, and 0 mass% to 90 mass% of a polycarbonate (A-2) except the copolymer (A-1); and an additive comprising a UV absorber, wherein a content of sodium in the polycarbonate-based resin composition is 0.5 ppm or less, wherein the sodium content is determined by calculation from the remaining amount of sodium determined by inductively coupled plasma spectrometry and the amount of each component blended into the composition: wherein: R 1 and R 2 each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, X represents a single bond, an alkylene group having 1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, a cycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a fluorenediyl group, an arylalkylene group having 7 to 15 carbon atoms, an arylalkylidene group having 7 to 15 carbon atoms, -S-, -SO-, -SO 2 -, -O-, or -CO-, and a and b each independently represent an integer of from 0 to 4; and R 3 and R 4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and n represents an average number of repetitions. R 1 and R 2 each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, X represents a single bond, an alkylene group having 1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, a cycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a fluorenediyl group, an arylalkylene group having 7 to 15 carbon atoms, an arylalkylidene group having 7 to 15 carbon atoms, -S-, -SO-, -SO 2 -, -O-, or -CO-, and a and b each independently represent an integer of from 0 to 4; and R 3 and R 4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and n represents an average number of repetitions.