PURPOSE: To obtain a semiconductor laser device having stable monitor currents, which are hardly changed with time, and high reliability by preventing the protrusion of gold-tin solder formed at the time of the temperature rise of die bonding to the rear of a semiconductor laser element by a gold film formed outside a tin film on the sub-mount side.

CONSTITUTION: A gold film 7, a tin film 8 and a gold film 9 are formed in sandwich structure on the underside of a sub-mount 2 and a gold film II, a tin film 10 and a gold film 13 on a semiconductor-laser element 3 placing section on the top face of the sub-mount 2. Gold films 11, 12, 13 are formed outside the semiconductor-laser element 3 placing section on the top face of the sub- mount 2. The tin films 8, 10 form gold-tin solder among the tin films 8, 10 and the gold films 7, 9, 11, 13 at the time of the temperature rise of die bonding. However, since the area of the tin film 10 is made smaller than that of a semiconductor laser element 3 and the area of gold-tin solder after the completion of die bonding is also made smaller than that of the semiconductor laser element 3, only the gold films 12 appear on the rear 1 of the semiconductor laser element 3, thus preventing the protrusion of gold-tin solder.