An adhesive composition for bonding optical parts comprising (A) 3 to 60 wt% of an epoxysilane or a hydrolysis/polycondensation product thereof, (B) 5 to 90 wt% of a bisphenol type epoxy resin having a viscosity of 2,000 to 5,000 mPa.s, (C) 5 to 35 wt% of a novolak type epoxy resin, 3 to 30 wt% of a curing agent which is an amine, and water and an alcohol in an amount of 0 to 0.75 time the total number of mols of the hydrolyzable groups or atoms of the epoxysilane. This composition has excellent moisture resistance and heat resistance, suppresses the formation of bubbles during curing, is free from such a defect as opaqueness caused by bubbles and can be used for the assembly and bonding of optical parts.