Abstract: A flame-retardant resin composition, which has a high flame retardancy equivalent to that of PVCs and can be separated from PVCs by a difference in specific gravity, is obtained by adding not less than 5 parts by weight and less than 50 parts by weight of a hydrated inorganic compound and not less than 1 part by weight and not more than 55 parts by weight of an auxiliary flame retardant having an action of forming a char-like thermally insulating layer on combustion and/or an action of foaming at high temperature thereby to entrap water vapor in a polyolefine resin so that the resulting flame-retardant resin composition has a specific gravity of 1.14 or less and an oxygen index of 24 or more.