Optical waveguide apparatus includes a two-dimensional optical waveguide, a light transmitting unit for transmitting light through the optical waveguide, a light receiving unit for receiving light transmitted through the optical waveguide, and a relaying unit for relaying light transmitted through the waveguide from the light transmitting unit at a place between the light transmitting unit and the light receiving unit to transmit the relayed light to the light receiving unit with the apparatus, the arrangement and flexibility of a light emitting device for converting an electrical signal into an optical signal and light receiving device for converting an optical signal into an electrical signal is large, and an optical transmission can be effectively performed.