An epoxy resin composition including an epoxy resin and a curing agent as essential components, in which the curing agent comprises a phenol resin which has each structural moiety of a phenolic hydroxyl group-containing aromatic hydrocarbon group (P), an alkoxy group-containing aromatic hydrocarbon group (B) and a divalent aralkyl group (X), and also has, in a molecular structure, a structure in which the phenolic hydroxyl group-containing aromatic hydrocarbon group (P) and the alkoxy group-containing aromatic hydrocarbon group (B) are bonded with the other phenolic hydroxyl group-containing aromatic hydrocarbon group (P) or alkoxy group-containing aromatic hydrocarbon group (B) via the divalent aralkyl group (X).