To realize the easy storage of waste formed polystyrene materials by reducing their volumes and, at the same time the high transportation efficiency and turn the waste foamed polystyrene materials into a recyclable stock by a method wherein the waste foamed polystyrene materials are crushed or cut into chips and then charged in the body part of a tower so as to blow hot air upon the chips therein.

At a cutting part 1, waste foamed polystyrene materials 9a are crushed or cut into chips 9b so as to be charged from the lower part 121 of a hopper through a piping 13 into the body part of a tower. Further, the supply port 24 of hot air is provided at a cylindrical part near a conical part 26. The hot air is guided from a hot air oven 31 through a duct 33 and the supply port 24 into the tower. The temperature of the hot air is properly adjusted in accordance with the size, expansion ratio and the like of the chip 9b intending to reduce its volume. Furthermore, the hot air is spirally moved in the tower and discharged from a discharging port 25 provided at the upper part of the main body of the tower outside the tower. During the discharging process of the hot air, the chips 9b in the course of their falling are sprayed with the hot air, resulting in turning into volumetrically reduced bodies 9c through the shrinkage of their volumes so as to be successively taken out of a valve 27. In addition, an agitator 28 agitates naturally falling chips 9b, resulting in accelerating the reduction of their volumes.