PURPOSE:To obtain heat-resistant-resin impregnant composition, consisting of a vinyl based monomer containing an epoxy acrylate, having improved heat resistance of cured articles of the impregnant and capable of improving characteristics of heat-resistant materials having voids, e.g. cast articles, sintered metals, ceramics, etc. CONSTITUTION:An impregnant composition, obtained by containing preferably 2-90wt% epoxy acrylate in a vinyl based monomer, preferably (meth)acrylate. The content of the epoxy acrylate is preferably 2-30wt% since a low-viscosity resin impregnant is suitable for cast aluminum articles, etc., having extremely fine voids in the structure thereof. A high-viscosity resin impregnant is suitable for sintered metals, etc., having a high void ratio and the content of the epoxy acrylate is preferably 30-90wt%.