PURPOSE: To improve the heating efficiency extending from an electric heater to a heat accumulating material, and also, to improve the warming efficiency by executing satisfactorily heat conduction extending from the heat accumulating material to the upper plate which becomes the warming surface.

CONSTITUTION: The warmer is constituted by filling the inside of a heat accumulating material vessel 1 with a heat accumulating material 3, and provided with an electric heater 2. In the heat accumulating material vessel 1, the electric heater 2 is arranged so as to be embedded into the heat accumulating materiel 3. On the reserse side of the upper plate 4 positioned in the upper part of the heat accumulating material vessel 1, plural fins 5 are provided projectingly, and the fins 5 are inserted into the heat accumulating material 3.