Provided is a photo-curable transparent resin in which an oxetane monomer for promotion of photo-curing, control of viscosity, and improvement of physical properties is mixed with a photo-cationically polymerizable cyclo-aliphatic epoxy group-containing oligosiloxane resin prepared by a sol-gel reaction. The photo-cationically polymerizable photo-curable transparent resin added with the oxetane monomer provides a cured product having high curing density and retaining excellent mechanical properties, thermal-mechanical properties, and electrical properties.