There is provided a semiconductor laser device capable of maintaining a good luminous characteristic under severe environment. A cap 4 in an approximate portal shape having lateral apertures 41 is attached to a stem 1 on which a laser diode 2 and a light receiving element 3 are mounted. A holographic element 5 is mounted on a window 43 of the cap 4. Air inside the cap 4 is exchanged with outside air through the lateral apertures 41 to effectively cool the laser diode 2, thus enabling the semiconductor laser device to maintain a good luminous characteristic under high-temperature severe environment.