An electro-optical circuit board (EOCB) in which an optical waveguide for transmitting an optical signal, and a driving unit/receiving unit and an optical source/optical detector for converting an electrical signal into the optical signal, and vice versa are integrated. The EOCB has a structure from which a lens is excluded for the purpose of an economical and efficient optical coupling between the optical waveguide and the optical source/optical detector. The optical source/optical detector are buried within a trench of a metal optical bench. The optical waveguide is then attached on the surface of the optical source/optical detector by means of an epoxy.