NOVELTY - A thermal storage material (1) has a porous base material (1a) and a thermal storage material composition (5a) impregnated in the base material. The composition contains a latent heat storage material and a hydrogenated styrenic thermoplastic elastomer. The weight average molecular weight of the hydrogenated styrenic thermoplastic elastomer is (5-17)x 104. The elastomer is contained in the ratio of 5-25 parts mass with respect to 100 parts mass of the latent heat storage material. The amount (Y') and the weight average molecular weight (X) of the elastomer satisfy specific relations.    USE - Thermal storage material used as building material e.g. floors, ceiling, roofs, inner walls and outer walls.    ADVANTAGE - The thermal storage material has suppressed leakage of the latent heat storage material impregnated in the porous base material.    DETAILED DESCRIPTION - A thermal storage material has a porous base material and a thermal storage material composition impregnated in the base material. The composition contains a latent heat storage material and a hydrogenated styrenic thermoplastic elastomer. The weight average molecular weight of the hydrogenated styrenic thermoplastic elastomer is (5-17)x 104. The elastomer is contained in the ratio of 5-25 parts mass with respect to 100 parts mass of the latent heat storage material. The amount (Y') of the elastomer and the weight average molecular weight (X) of the elastomer satisfy the relations: Y' greater than or equal to (-2-X+25), when X is (5-10)x 104 (including 5), and Y' less than or equal to (-5-X+90), when X is (14-17)x 104 (excluding 14). An INDEPENDENT CLAIM is included for manufacture of the thermal storage material, which involves melting the thermal storage material composition, and permeating the obtained molten liquid into the base material.    DESCRIPTION OF DRAWING(S) - The drawing shows an explanatory view of the manufacture of thermal storage material.    Thermal storage material (1)    Porous base material (1a)    Thermal storage material composition (5a)    Tank (9)