A rubber-modified flame resistant styrene resin composition, which has superior heat stability and weather resistance to prevent discoloration and deterioration due to heat or light and is processed under various molding condition, is provided. The rubber-modified flame resistant styrene resin composition includes a rubber-modified styrene resin, flame retardant comprising compounds selected from a group consisting of tetrabromobisphenol-A-bis(2,3-dibromopropylether), hexabromocyclododecane and a mixture thereof, and brominated epoxy oligomer, and calcium stearate as a lubricant.