PROBLEM TO BE SOLVED: To provide a polystyrene resin extruded foam plate having high flame retardancy against more severe conditions, especially against contact with sparks. A polystyrene resin extruded foam plate obtained by extruding a polystyrene resin by using a physical foaming agent, wherein the physical foaming agent is an aliphatic saturated hydrocarbon having 3 to 5 carbon atoms and hydrofluorocarbon. A physical foaming agent containing an olefin and another foaming agent, wherein the total amount of the saturated aliphatic hydrocarbon having 3 to 5 carbon atoms and the hydrofluoroolefin is 0.30 to 1.10 mol per 1 kg of the polystyrene resin. The ratio of the blending amount of the aliphatic saturated hydrocarbon having 3 to 5 carbon atoms to the total blending amount of 100 mol% is 0.5 mol% or more and less than 10 mol%, and the surface layer portion from the surface of the extruded foam plate to 5 mm in the thickness direction. The ratio ((I)/(II)) of the apparent density (I) to the apparent density (II) of the entire extruded foam plate exceeds 1.10. [Selection diagram] None
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