An optical transmission module has an optical wiring for transmitting light, and an optical element for irradiating a light incidence plane of the optical wiring with light and a control circuit component for driving light emission of the optical element based on an externally input electric signal, or an optical element for receiving light emitted from a light emitting surface of the optical wiring and converting to an electric signal and a control circuit component for amplifying the electric signal output from the optical element and outputting to the outside. A plurality of boards overlapped and stacked so as to form a step with each other is arranged. A first board stacked at one end in a stacking direction of the plurality of boards is mounted with the optical wiring and the optical element so as to sandwich both surfaces in the stacking direction, and a board surface on the first board side of a second board stacked at another end is mounted with the control circuit component.