An epoxy resin represented by the following formula (1) wherein R1 represents an alkylene group having 2 to 6 carbon atoms and optionally containing an ester or ether bond; R2 represents a monovalent aliphatic hydrocarbon group having 1 to 6 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms; R3 represents an oxygen atom or a phenylene group; k represents 1 to 10 as an average value; m represents an integer of 0 to 2; n represents 0 to 10 as an average value; and a plurality of groups R1, R2, R3, k, or m present in the formula may be the same or different from each other.