A heat storage system is provided that is capable of being manufactured at lower cost and has higher heat transmission efficiency. A heat storage system includes a heat storage material having a higher specific gravity in a solid phase than in a liquid phase, a heat storage tank for containing the heat storage material, a cooling side heat exchanger arranged at an upper section inside the heat storage tank and for cooling the heat storage material, a heating side heat exchanger arranged at a lower section inside the heat storage tank and for heating the heat storage material, and a wall surface heater for heating a side wall of the heat storage tank.