To provide a structure of a compact electric water heater, whose stainless steel vessel is not required to be covered with a heat insulating material, such as glass wool or the like, at its outer surface, with its design not being damaged.

The water heater has a vacuum dual structure of substantially a cylindrical shape consisting of an inner vessel and an outer vessel with the space therebetween being evacuated. Either or both of the ends of the panel boards of the dual-structure vessel is/are attached with a water supply pipe, a hot water supply pipe and an electric heater by a joining means, such as welding or the like.