To provide a semiconductor laser device of monolithic structure which is capable of separately driving laser rays of different wavelengths and suitable for reading out data stored in an optical disk.

This semiconductor laser device is composed of a first laser diode which is equipped with two clad layers 3 and 5 and a first active layer 4 sandwiched by the clad layers 3 and 5 formed on a substrate 2 and emits laser rays from the edge face of the first active layer 4 and a second laser diode which is equipped with two clad layers 9 and 11 formed on a part of the first laser diode and a second active layer 10 sandwiched by the clad layers 9 and 11 and projects laser rays whose wavelength is different from that of the first laser diode from the edge face of the second active layer 10.