The aim of the invention is to provide technology for accurately transmitting information between circuit boards, wherein the optical signal is used as information medium. A fixing member (10) fixes aplurality of circuit boards (20) with prescribed intervals, and optical communication paths are provided among the circuit boards (20). The fixing member (10) is provided with a main body (15) and anoptical waveguide (12) penetrating the main body (16). The fixing member further comprises a light receiving section (50) and a light emitting section (40). Through the fixing member (10), the lightsignal which is emitted from one circuit board (20) and is received by another circuit board (20) is transmitted along the optical waveguide (12) of the fixing member (10).