Epoxy resin composition and cured article thereof, semiconductor encapsulation material, novel phenol resin, and novel epoxy resin

The object of the present invention is to provide an epoxy resin composition capable of realizing low dielectric constant and low dielectric dissipation factor, which is suited for use as a latest current high-frequency type electronic component-related material, without deteriorating heat resistance during the curing reaction. A phenol resin, which has the respective structural units of a phenolic hydroxyl group-containing aromatic hydrocarbon group (P) derived from phenols, an alkoxy group-containing condensed polycyclic aromatic hydrocarbon group (B) derived from methoxynaphthalene and a divalent hydrocarbon group (X) such as methylene and also has a structure represented by -P-B-X- wherein P, B and X are structural sites of these groups in a molecular structure, is used as a curing agent for the epoxy resin, or a phenol resin as an epoxy resin material.