PURPOSE: To process optical signals by an efficient method by attaining an optical waveguide structure inside a circuit board capable of maintaining the optical form until input signals reach individual devices on the board.

CONSTITUTION: The circuit board 10 is provided with an optical waveguide structure extended adjacently to the upper surface 12. The optical waveguide structure is composed of three shapes provided with a normal main trunk 18, the two branches of a first level and the four branches of a second level. Further, the end part of an optical fiber 24 for transmitting input optical signals to this assembly and the base of the optical waveguide structure are both flatly ground and held so as to be in contact with each other. Thus, the optical signals are transmitted through the optical waveguide structure to plural chips 14. Also, the respective chips 14 for requesting data reception from the optical waveguide structure are provided with a photodiode 26. The photodiode 26 receives the optical signals from the part adjacent to the respective chips of the optical waveguide structure and then, the received signals are converted to electric signals by a processing by a circuit inside the chip.