In an optical communications module comprising one or more dielectric substrates equipped with an optical transmitter section, an optical receiver section or an optical transceiver section, and a chassis encasing all of them, a metal part is formed on one side of at least one of the dielectric substrates such that the metal part constitutes the whole or a part of the exterior surface of the chassis so that the length of heat conduction from a dielectric substrate with heat-generating components installed thereon can be minimized so as to efficiently release heat through the metal part to outside, curbing a temperature increase within the chassis. Thus, the optical communications module can exhibit excellent performance.