PURPOSE: To produce an uniform heat accumulating composite material by mixing the heated and molted heat accumulating material of the latent heat type with unvulcanized liquid high molecular weight substance.

CONSTITUTION: To disperse latent heat type-heat accumulating material uniformly in a high molecular weight substance, both specific gravities must be substantially equal. Therefore, 50wt part carbon black is uniformly mixed with 100wt part liquid silicon rubber, and the specific gravity of said mixture is regulated to be 1.3. Next, into this material, the solution, which is heated at 60°C of the heat accumulating material of latent heat type (sodium acetate 3, hydrate) with equal weight, is added with agitation, and both materials are mixed uniformly. After the heat accumulating material has been solidified under heating, this gel-like mixture is poured in a mold and heated at 50°C four hours, whereby silicon rubber is solidified, and thus the heat accumulating composite material with uniform emission of latent heat as a whole may be produced.