PURPOSE: To prevent the entry of air into a foaming resin heat insulating material and maintain a mechanical strength as well as a heat insulating characteristic for a long period by providing a protective layer having a gas barrier characteristic on a surface facing a door inner plate made of the foaming resin heat insulating material.

CONSTITUTION: In a door 1, a vacuum heat insulating material 5 is bonded to a metallic outer plate 3, a sash 4 made of a resin is fitted thereto and a foaming resin heat insulating material 8 such as foaming urethane is injected and solidified in a foaming jig in which the outer plate 3 and the sash 4 are housed so that the vacuum heat insulating material 5 is buried therein. A protective layer 12 having a gas barrier characteristic is formed on the surface of the foaming resin heat insulating material 8 facing a door inner plate 9. A plastic film low in its thermal conductivity is suitable for the material of the protective layer to prevent the entry of heat from the sash 4. The protective layer is formed by setting the outer plate 3, the sash 4 and the vacuum heat insulating material 5 together in the foaming jig when the foaming resin heat insulating material 8 is injected and solidified, and injecting or applying a resin such as polyvinylidene to the surface thereof after the foaming resin heat insulating material 8 is injected and solidified to form a coated layer.