To provide an epoxy resin composition that reveals excellent flowability, moreover its cured product reveals excellent heat-resistance.

The method for producing the cured product comprises heating an epoxy resin composition whose essential components are an epoxy resin (A) having an alicyclic structure, an acid group-containing radically polymerizable monomer (B), and a radical polymerization initiator (C), and performing reaction of an epoxy radical of the epoxy resin (A) with an acid radical of the monomer (B), and simultaneously performing polymerization caused the radically polymerizable group of the monomer (B).