An optical transmission device has a light emission element for converting an electrical signal to an optical signal to transmit it to an optical fiber; a lead frame for mounting the light emission element and having a through hole at a position determined with reference to a mounted position of the light emission element; and a receptacle having a protrusion portion inserted in the through hole to fix a position of the lead frame relatively, and a sleeve into which an end portion of the optical fiber is inserted to fix a position of the optical fiber relatively, the receptacle optically connecting the light emission element and the optical fiber.