Disclosed is a silicone-modified epoxy resin (D) including a structural unit represented by following Formula (4). The epoxy resin (D) is a product of the epoxidation of a vinyl group of a vinyl-containing polyether compound (C) with an oxidizing agent, the vinyl-containing polyether compound (C) has a structural unit represented by following Formula (3) and is a product of the reaction between an epoxy group of 4-vinylcyclohexene-1-oxide (A) represented by following Formula (1) and a silanol group of a silanol-containing organopolysiloxane (B) represented by following Average Compositional Formula (2). The silicone-modified epoxy resin is a polyfunctional cycloaliphatic epoxy resin having an oxycyclohexane skeleton and being improved in thermal stability and hygroscopicity absorptivity. In Formula (2), “a” is 0.01 to 1.99; “b” is 1.99 to 0.01; and R is a residue of monovalent organic compound having one to nine carbon atoms, and the vinyl group in Formula (3) and the epoxy group in Formula (4) are bound at the alpha-position or the beta-position in Formulae (3) and (4), respectively.