A light wavelength converting apparatus includes a semiconductor laser having gain, phase, and DBR regions, a nonlinear optical device for receiving fundamental-wave light emitted from the semiconductor laser and outputting second harmonic wave light, a first optical detector for monitoring output of the fundamental-wave light, a second optical detector for monitoring the second harmonic wave light, and a control portion for controlling a drive current for driving the semiconductor laser. The control portion includes a control parameter determiner and wavelength controller. The control parameter determiner changes a DBR current supplied to the DBR region and a phase current supplied to the phase region to obtain a changing point, and determines a control parameter for controlling the DBR and phase currents such that the relationship therebetween is not located on the changing point. The wavelength controller controls the DBR and phase currents pursuant to the control parameter.