To improve heat-retaining performance, be light-weighted, and excellent in economic efficiency by taking a metal excellent in thermal conductivity as a matrix, joining a raw material which has lower specific gravity and lower thermal conductivity than the metal to the outer peripheral part, and making at least a part of a joined part of the metal and low thermal conductive raw material as a complex by combining the metal and the raw material.

A container main body 1 of a heat insulating cooker is provided with a heat transfer part 2 formed of a metal excellent in thermal conductivity, which is disposed in the inner part of the container. Further, the outside of the container is provided with a heat insulating part 3 formed of a raw material which has a lower specific gravity and lower thermal conductivity. Further, in a joining part between the heat transfer part 2 formed of the metal excellent in thermal conductivity and the heat insulating part 3 formed of the low thermal conductivity raw material, there is provided a portion where the metal excellent in thermal conductivity enters voids of the low thermal conductivity raw material, that is, a complex part 4. The complex part 4 may be formed partially or uniformly, and further preferably it may be formed with a gradient. The joint strength of the metal excellent in thermal conductivity and the low thermal conductive raw material is enlarged by such complex.