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.