To provide a latent heat accumulating material which has a great heat accumulating capacity, has such a high heat conductivity as to rapidly absorb and emit heat, can be produced without being accompanied by defects of an impregnating method, and is based on a phase change material.

The heat accumulating material contains a mixture of a phase change material with particulate expanded graphite. A paraffin, a sugar alcohol, a gas hydrate, water, or the like can be used as the phase change material. The addition of a nucleating agent such as tetrasodium diphosphate decahydrate or sodium hydrogenphosphate to the accumulating material prevents its supercooling in its coagulation.