An extruded styrene resin foam obtained by extrusion-foaming of a styrene resin and excellent in environmental compatibility and excellent in flame retardant property and thermal insulating property, characterized in that it contains, as a blowing agent, 100 to 10% by weight of at least one of saturated hydrocarbons having 3 to 5 carbons and 0 to 90% by weight of other blowing agent, based on the total amount of the blowing agent, and contains (A) a halogenated flame retardant and (B) at least one compound selected from the group consisting of phosphorus type flame retardants containing nitrogen atom in a molecule, tetrazole compounds, cyanuric acid and derivatives thereof, isocyanuric acid and derivatives thereof, metal borates, and boron oxides.