An optical waveguide device comprises a first under-cladding layer, a light emitting element provided on an upper surface of the first under-cladding layer and having a light emitting portion which emits light, and a core provided on the upper surface of the first under-cladding layer and having a light receiving portion which receives the light emitted from the light emitting portion of the light emitting element. The light receiving portion of the core has a generally U-shape as seen in plan, and the emitted light is projected into an opening of the generally U-shaped light receiving portion.