Disclosed herein is a light source device and a wavelength control device therefor. The light source device includes a plurality of laser diodes, a temperature sensor provided in the vicinity of the plurality of laser diodes, a control loop for controlling the temperatures of the plurality of laser diodes according to an output from the temperature sensor to thereby control the oscillation wavelengths of the plurality of laser diodes, and a unit for compensating temperature control conditions for the laser diodes other than a reference laser diode selected from the plurality of laser diodes, according to a change in temperature control condition for the reference laser diode. By the compensation of the temperature control conditions, the oscillation wavelength of each laser diode can be easily stabilized to each wavelength channel of WDM.