PURPOSE: To obtain the title material excellent in thermal conductivity and less abrasive to a mold, by mixing an epoxy resin with BN and spherical alumina and optionally a crosslinking agent, a cure accelerator, a curing agent a mold release, a colorant, a coupling agent, etc.

CONSTITUTION: A curable epoxy resin (A) is mixed with BN and spherical alumina (B) of a mean particle diameter ≤10μ, preferably surface-treated with a organopolysiloxane, and optionally a cure accelerator based on a phosphorus compound and/or a tert. amine, a curing agent, a crosslinking agent, a mold release, a colorant, a coupling agent, a filler other than B, etc., and the obtained mixture is kneaded, ground and optionally granulated.