To provide a heat accumulator and a heating system of the heat accumulator, which maintains a predetermined temperature over a long time, and performs heat accumulating work in a short period of time without requiring so much labor.

A powdery heat accumulating material 11 is arranged in the heat accumulator 10, and each powder grain 11a of the heat accumulating material 11 is composed of a core material 11b and a capsule member 11c, and since the core material 11b changes in a phase to a liquid phase from a solid phase at the predetermined temperature, the heat accumulator 10 maintains the predetermined temperature over the long period. Since an outside member 11e of the capsule member 11c of the respective powder grains 11a is composed of a metallic material heatable by electromagnetic induction, the whole heat accumulator 10 is heated in a short period of time by the electromagnetic induction regardless of a quantity of the heat accumulator 10.