The object of the present invention is to provide a technique for accurately transmitting information, wherein optical signals are the medium of information, between circuit boards.A holding member 10 taught in the present specification holds a plurality of circuit boards 20 with a predetermined distance therebetween, and provides an optical communication path between the circuit boards 20. The holding member 10 comprises a body 15 and an optical waveguide 12 that penetrates the body 15. The holding member 10 further comprises a light receiving portion 50 and a light emitting portion 40. By means of the holding member 10, an optical signal emitted at one circuit board 20 and received at an other circuit board 20 travels along the optical waveguide 12 of the holding member 10.