Abstract: Plastic foam has excellent heat insulation properties, however, moisture absorption is causing a decrease in the heat insulation, and plastic foam has almost no mechanical strength. Therefore, a heat insulation material that absorbs almost no moisture and has satisfactory strength is desired to appear. According to the present invention, a foam composite with a skin can be formed in one shot by charging plastic powders or minute particles together with polyolefin pellets that can be cross-linked and foamed in a mold, and heating the mold while rotating. The composite absorbs almost no moisture, having satisfactory strength, being excellent as an insulating material. Further, providing a covering of a non-foaming or a slightly foaming material to the pellet of polyolefin that can be cross-linked and foamed, and conducting the forming, foamed granules of preferably 5 to 50 mm largeness as a core, and a covering of a reinforcing member with 0.05 to 0.