an optical transmission module includes : a substrate ; an electric wiring section that is provided on the substrate ; a photoelectric element that are mounted on the electric wiring section , and that emits an optical signal on the basis of a received electric signal or transmits an electric signal on the basis of a received optical signal ; an optical part that comprises at least one of an optical conversion section and an optical fiber receptacle section , and that controls an optical path of optical signal between the photoelectric element and an optical fiber ; a mounting support member that positions the photoelectric element ; and a positioning mechanism that positions the optical part and the mounting support member .