The thermoset optical-purpose adhesive according to the present invention, having a superior resistance to heat and moisture and a high transparency is a mixed adhesive which is mainly composed of a primary agent and a curing agent, and is characterized by having a visible-ray transmittance of 90% or more after heat curing under conditions of a layer thickness that is enough for the adhesive to function as an adhesive. It is also characterized in that the primary agent is constituted of a silane modified epoxy resin whose active-radical moieties other than epoxy radicals have been inactivated in part or in entirety by the aid of a metallic soap and to at least one epoxy radical of which a silane coupling agent has been attached, and the curing agent is constituted of an amine type compound or an amide type compound.