A flame-retardant resin composition characterized by comprising: a styrene-based resin; a brominated polymer type flame retardant; an epoxy compound; a halogen capture agent; and an antioxidant, wherein the content of bromine is 18 to 42% by mass; 4 to 25 parts by mass of the epoxy compound, 0.8 to 15 parts by mass of the halogen capture agent, and 0.8 to 7 parts by mass of the antioxidant based on a total of 100 parts by mass of the styrene-based resin and brominated polymer type flame retardant are contained; the halogen capture agent contains at least either of a dolomite-based compound and a hydrotalcite-based compound; and the brominated polymer type flame retardant has the following features (a) to (f), (a) the brominated copolymer is a copolymer having butadiene and vinyl aromatic hydrocarbon as a monomer component; (b) the content of the vinyl aromatic hydrocarbon monomer in the copolymer before bromination is 5 to 90% by mass; (c) 1,2-butadiene is contained in butadiene; (d) the weight average molecular weight (Mw) is 1000 or more; (e) the content of unbrominated nonaromatic double bonds determined by 1 H-NMR spectroscopy is less than 50% based on the content of the nonaromatic double bonds of the copolymer before bromination; and (f) the 5% weight reduction temperature obtained by thermogravimetric analysis is 200°C or higher. a styrene-based resin; a brominated polymer type flame retardant; an epoxy compound; a halogen capture agent; and an antioxidant, wherein the content of bromine is 18 to 42% by mass; 4 to 25 parts by mass of the epoxy compound, 0.8 to 15 parts by mass of the halogen capture agent, and 0.8 to 7 parts by mass of the antioxidant based on a total of 100 parts by mass of the styrene-based resin and brominated polymer type flame retardant are contained; the halogen capture agent contains at least either of a dolomite-based compound and a hydrotalcite-based compound; and the brominated polymer type flame retardant has the following features (a) to (f), (a) the brominated copolymer is a copolymer having butadiene and vinyl aromatic hydrocarbon as a monomer component; (b) the content of the vinyl aromatic hydrocarbon monomer in the copolymer before bromination is 5 to 90% by mass; (c) 1,2-butadiene is contained in butadiene; (d) the weight average molecular weight (Mw) is 1000 or more; (e) the content of unbrominated nonaromatic double bonds determined by 1 H-NMR spectroscopy is less than 50% based on the content of the nonaromatic double bonds of the copolymer before bromination; and (f) the 5% weight reduction temperature obtained by thermogravimetric analysis is 200°C or higher. (a) the brominated copolymer is a copolymer having butadiene and vinyl aromatic hydrocarbon as a monomer component; (b) the content of the vinyl aromatic hydrocarbon monomer in the copolymer before bromination is 5 to 90% by mass; (c) 1,2-butadiene is contained in butadiene; (d) the weight average molecular weight (Mw) is 1000 or more; (e) the content of unbrominated nonaromatic double bonds determined by 1 H-NMR spectroscopy is less than 50% based on the content of the nonaromatic double bonds of the copolymer before bromination; and (f) the 5% weight reduction temperature obtained by thermogravimetric analysis is 200°C or higher.