The present invention provides an epoxy resin solution, from which an epoxy resin-cured product adequately excellent in heat-resisting properties and dielectric properties can be obtained with adequately good working properties ensured. The present invention relates to an epoxy resin solution containing at least a curing agent and an epoxy resin mixed in an organic solvent, wherein the curing agent comprises an imide group-containing curing agent having 1-4 imide groups and 2-4 glycidyl group-reactive functional groups in a molecule.