provided is a method for producing glass - fiber - reinforced molded resin foam which retains intact material properties inherent in glass - fiber - reinforced molded resins , has a finely and evenly foamed state , and has excellent mechanical strength , and which can be reduced in weight . the method for producing glass - fiber - reinforced molded resin foam comprises subjecting a resin , flat glass fibers , and a blowing agent to injection molding .