Disclosed are a method of manufacturing a wiring board including, in order of mention, step A of fabricating a circuit on a first board, step B of providing a first support over the circuit fabrication surface of the first board with a first separation layer therebetween, and step C of providing a second board or a circuit on the opposite side of the circuit fabrication surface of the first board and a method of manufacturing an optoelectric composite member including, in order of mention, a step of providing an electric wiring board on a second support, a step of providing a first support, a step of removing the second support, and a step of fabricating an optical waveguide on the separation surface of the second support. The method of manufacturing the wiring board enables fabrication of the circuit with uniform wiring width and good dimensional stability. The method of manufacturing an optoelectric composite member enables reduction of distortion of the optical waveguide during the manufacturing steps, thereby improving the dimensional stability.