To provide a variable wavelength laser light source which can be manufactured with high productivity, has a simple constitution, and is highly stable.

A nonreflective film 7a and a highly reflective film 7b are respectively formed on the front and rear end faces of a laser diode 1, and the light emitted form the diode 1 is demultiplexed by making the light incident to a multiplexer/demultiplexer 3a after the light is condensed through a lens 2. Then, a wavelength selecting section 4 selects the light having a specific wavelength λa, and a light feeding-back section feeds back the selected light to the diode 1 through multiplexers/demultiplexers 3c and 3c after the light is condensed through the lens 2. An external resonator composed of the light feeding-back section and the highly reflective film 7b emits laser light by resonating the fed-back light, and the laser light is fetched from an output port 5 through a multiplexer/demultiplexer 3d.