Disclosed is a heat dissipating material which is interposed between a heat-generating electronic component and a heat dissipating body. This heat dissipating material contains (A) 100 parts by weight of a silicone gel cured by an addition reaction having a penetration of not less than 100 (according to ASTM D 1403), and (B) 500-2000 parts by weight of a heat conductive filler. Also disclosed is a semiconductor device comprising a heat-generating electronic component and a heat dissipating body, wherein the heat dissipating material is interposed between the heat-generating electronic component and the heat dissipating body.