To provide a heat insulator with a vacuum layer simply formed into a free shape, having high sealing reliability, even when bent, and superior heat insulating property and recycling property.

A plurality of metal plates 1, 2 are superimposed on each other with their printed faces 3 as inner faces, non-printed faces 4, 5 between the metal plates 1, 2 are joined to each other by rolling, and a mouth portion 21 is provided in the printed face 3 in communication with outside air. Compressed air is filled through the mouth portion 21 to form an expanded sealed space 31 and then the mouth portion 21 is degassed to form the sealed space as the depressurized vacuum layer 15. The mouth portion 21 is blocked with e.g. soldering.