To provide an impregnation resin composition having a good soldering property, holding electrical, mechanical, and curing characteristics at the conventional level, and having a good balance and to provide an electric apparatus impregnated with it.

This impregnation resin composition comprises a methylene diisocyanate denatured unsaturated polyester resin (A) and a polymerized monomer (B) as essential components. Methylene diisocyanate is contained at the ratio of 40-90 wt.% in the methylene diisocyanate denatured unsaturated polyester resin (A), and the polymerized monomer (B) is blended at the ratio of 100-400 wt.% against the methylene diisocyanate denatured unsaturated polyester resin (A). An electric apparatus such as a pin type transformer is impregnated with this impregnation resin composition.