An optical transmission module includes: a photoelectric conversion element that converts an electrical signal to an optical signal; a photoelectric conversion element-driving IC that drives the photoelectric conversion element; an optical fiber that transmits the optical signal; a guide holding member that holds the optical fiber; a cable that supplies power to at least one of the photoelectric conversion element and the photoelectric conversion element-driving IC; and a substrate on which the photoelectric conversion element and the photoelectric conversion element-driving IC are mounted. The substrate has first and second planes which are perpendicular to each other. The photoelectric conversion element is mounted on the first plane. The optical fiber is connected to a back side of the first plane. An optical axis of the optical fiber is perpendicular to the first plane. The cable is connected to the second plane in parallel with the optical axis of the optical fiber.