An epoxy resin composition comprising all of following components to:: reactive diluent having a structure represented by any one of the following general formulae, and and having a viscosity of 2 Pa•s or less at 25°C; in the general formula, R 3 and R 4 each independently represent at least one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group; and X 3 represents one selected from the group consisting of -O-, -S-, -CO-, -C(=O)O- and -SO 2 -, in the general formula, R 7 and R 8 each independently represent at least one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group, with the proviso that both of R 7 and R 8 are not hydrogen atoms, in the general formula, R 9 and R 10 each independently represent a direct bond, an alkylene group with a carbon number of 1 to 8, a phenylene group or a cyclohexylene group; and R 11 represents one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group,: trifunctional or higher functional epoxy resin; and: at least one amine-based hardener selected from the group consisting of an amine-based hardener having a structure represented by following general formula and an amine-based hardener having a structure represented by following general formula: in the general formula, R 1 represents a hydrocarbon group with a carbon number of 2 to 4; and in the general formula, R 2 represents a hydrogen atom or an amino group.: reactive diluent having a structure represented by any one of the following general formulae, and and having a viscosity of 2 Pa•s or less at 25°C; in the general formula, R 3 and R 4 each independently represent at least one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group; and X 3 represents one selected from the group consisting of -O-, -S-, -CO-, -C(=O)O- and -SO 2 -, in the general formula, R 7 and R 8 each independently represent at least one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group, with the proviso that both of R 7 and R 8 are not hydrogen atoms, in the general formula, R 9 and R 10 each independently represent a direct bond, an alkylene group with a carbon number of 1 to 8, a phenylene group or a cyclohexylene group; and R 11 represents one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group,: trifunctional or higher functional epoxy resin; and: at least one amine-based hardener selected from the group consisting of an amine-based hardener having a structure represented by following general formula and an amine-based hardener having a structure represented by following general formula: