Optical transmission module

This optical transmission module wires and connects a coaxial can package in which high-speed signal transmission wiring whose characteristic impedance matches is formed on a ceramic PC board into which a coaxial can stem penetrates and a PC board on which a peripheral circuit is mounted using a flexible PC board in which the high-speed signal transmission wiring is formed in the same manner. The module makes, on the opposite side, an elastic conductive heat-conducting material is interposed between the coaxial can package and a housing in which a radiating fin is formed and the conductive heat-conducting material or an elastic insulating heat-conducting material between a circuit component mounted on a PC board and the housing in which the radiating fin is formed intervene. The module forms a fitting structure in each of a ferule and a receptacle portion of a transmission module or receiving module and can rotate to the direction of an optical axis. The module provides a built-in isolator receptacle type optical transmission module having easy-to-assemble structure that realizes high-speed signal transmission and efficiently radiates the heat generated from the coaxial can package.