An insulated structure is formed by injection of a foamed thermal-insulating material created by foaming into a space between a plastic board and metal plate with a disposition of copper pipes. A non-halogenated organophosphorus compound having a molecular weight over 150 as an additive with an OH group as a functional group is mixed with the raw materials of the foamed thermal-insulating material including polyol, a foam stabilizer, a catalyst, a foaming agent having at least one component of hydrocarbon, and an organic polyisocyanates. By adding a non-halogenated organophosphorus compound, which has a molecular weight over 150 as an additive with an OH group as a functional group, the burning rate of the foamed thermal-insulating material becomes the same as that of the foamed thermal-insulating material which uses CFC11 as a foaming agent. Also, the possibilities of phosphor corrosion by free ionization to copper pipes, which are disposed inside of the insulated structure, are eliminated and phosphorus transfer to the plastic board and worries of food contamination are also eliminated.