Epoxy resins are widely used as structural and functional materials; however, controlling network architecture and crosslink density remains challenging in conventional epoxy systems. In this study, a multifunctional epoxy resin was synthesized using bisphenol A (BPA) and a trifunctional isocyanate, 1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione. The trifunctional isocyanate enables the formation of a three-dimensional structure through reactions with the phenolic hydroxyl groups of BPA. Subsequent epoxy functionalization produces epoxy resins capable of forming densely crosslinked thermoset networks. The resulting epoxy systems are expected to exhibit improved mechanical strength and thermal stability compared to conventional diisocyanate-based epoxy resins. This work presents an effective molecular design approach for high-performance epoxy networks using multifunctional structures.