In a semiconductor laser apparatus, semiconductor laser devices are mounted on a loading face of a radiation base portion produced from a radiation material in a mount board, and the radiation base portion and a cap portion constitute an envelope surrounding the semiconductor laser devices. Further, the radiation base portion and interconnections formed on and an extending face of the radiation base portion constitute an external connection terminal. Therefore, heat generated by the semiconductor laser devices is efficiently transferred to the radiation base portion produced from a radiation material. Further, constituting the external connection terminal allows a leadless configuration to be implemented. Thus, a semiconductor laser apparatus which is sufficient in radiation characteristics and is capable of supporting a low-profile specification is provided.