A semiconductor laser device aimed to be reduced in size and that can maintain high position accuracy, and a fabrication method of such a semiconductor laser device are achieved. A semiconductor laser device includes a stem as a base member, and a cap member. The stem includes a main unit having a reference plane, and a heat sink platform as an element mount unit, located on the reference plane for mounting a laser element. The cap member is set on the reference plane of the stem so as to cover the heat sink platform. A hole is formed at the sidewall of the cap member facing the heat sink platform. Fixation between the cap member and the stem is established by fixedly attaching the portion at the inner side of the sidewall of the cap member adjacent the hole to the outer circumferential plane of a heat sink platform.