A metal heat storage apparatus comprises a metal heat storage medium, a medium insertion chamber insulating the inner side, outer side and the floor of the metal heat storage medium; an outer wall structure made of concrete further insulating the metal heat storage medium and including a floor, a central column, an outer wall body, and an upper cover; an infrared ray reflecting mirror disposed below the upper cover constituting the outer wall structure and reflecting infrared rays generated from the metal heat storage medium; a heat exchanger spirally disposed inside the metal heat storage medium and including supply and drain tubes exposed to the outside of the outer wall structure; a solar heater buried in the metal heat storage medium; and a high-density optical input port passing through the outer wall body and the insulating outer wall to provide solar energy to the solar heater.