TECHNOLOGY FOCUS - POLYMERS - Preferred Foam: The composition of styrene resin foam further contains water absorptive substance, and halogenated flame retardant excluding the flame retardant (I), phosphorus-containing compound, nitrogen compound and/or boron-containing compound. The water absorptive substance is bentonite, hectorite and/or silica. The foam comprises gas bubble having diameter of 0.25 mm or less and gas bubble having diameter of 0.3-1 mm. Preferred Properties: The contents of 3-5C saturated hydrocarbon compound, water and non-freon-type foaming agent are 90-10 wt.%, 1-80 wt.% and 0-89 wt.%, respectively, with respect to whole quantity of foaming agent. The content of 3-5C saturated hydrocarbon compound with respect to 100 weight parts (wt.pts) of foam is 1-10 wt.pts. The content of flame retardant is 0.1-20 wt.pts with respect to 100 wt.pts of styrene resin. The occupied-area rate of the gas bubble having diameter of 0.25 mm or less is 5-95% per foam cross-section of the foam. SPECIFIC COMPOUNDS - The non-freon-type foaming agent is dimethyl ether, diethyl ether, methyl ethyl ether, methyl chloride, ethyl chloride and/or carbon dioxide. The 3-5C saturated hydrocarbon is propane, n-butane and/or i-butane. The flame retardant is tris-(2,3-dibromo propyl)isocyanurate.    EXAMPLE - Tris-(2,3-dibromo propyl) isocyanurate (in weight parts) (7), isocyanurate (3), isobutane (4), dimethyl ether (2), water (1), bentonite (1), AEROSIL (0.1), talc (0.5) and barium stearate (0.25), were mixed to obtain a resin mixture. The obtained resin mixture was supplied to an extruder by 70 kg/hour. The supplied resin mixture was heated at 200degreesC, melted, plasticized, kneaded and cooled to obtain an extrusion-foamed material of rectangular solid shaped. The obtained foamed material had foam thickness of 50 mm, foam density of 30 kg/m3, heat conductivity of 0.026 W/mK, and gas bubble of diameter 0.07 mm and area ratio 42%. The foamed material had excellent thermal insulation property, flame retardance, moldability and recyclability.