In an optical coupling device, a main waveguide have a linearly extending portion and a tapered portion formed on a first clad layer. The waveguide has a width which is gradually reduced towards an incident side of the light wave. Auxiliary waveguides are formed on the both sides of the main waveguide, wherein each of the auxiliary waveguides has first and second tapered portions having widths which are gradually reduced toward both sides. A second clad layer is so formed as to cover the main and auxiliary waveguides and first clad layer, wherein the first clad layer guides the light wave introduced into the first clad layer or the second clad layer and gradually converge the light wave towards the main waveguide.