Abstract: A process for producing a polystyrene resin foam is disclosed, which comprises supplying an extruding machine with a polystyrene resin, a fine inorganic powder and a highly volatile foaming agent, heating them to melt, and extruding the melt from the nozzle into a zone of the lower pressure, wherein 0.01 to 2 parts by weight of an alcoholic ester of a higher fatty acid is added to 100 parts by weight of the polystyrene resin. The process insures that foams having a skin of good aesthetic appeal that are free from staining and malodor can be produced consistently for a prolonged time without any fire hazard.