To provide a resin composition useful for coatings, adhesives and a material for cement having an excellent adhesion property, a rust proof property and chemical resistance.

The aqueous cationic epoxy resin composition comprises (A) amine modified epoxy resin, (B) an acid compound, (C) water soluble organic solvent and (D) water. The amine modified epoxy resin (A) is composed of an adduct of a epoxy resin having one or more epoxy groups in one molecular chain and multifunctional amine. The addition reaction is carried out in such a way as the molar ratio a1/a2 of active hydrogen (a1) in the multifunctional amine to the epoxy group (a2) is kept in the range of 1.0 and 2.0. The acid compound (B) is added of which the active hydrogen is in the range of 0.5-4.0 equivalent per 1.0 that of nitrogen in the amine modified epoxy resin (A).