A wavelength converter including a fiber provided with a laser active substance and formed with first and second fiber gratings embedded in the fiber, a laser light source that allows pumping light to be incident on the fiber, a laser resonator formed by optically connecting the fiber and the laser light source, and a wavelength conversion element that converts the fundamental wave of a laser beam emitted from the laser resonator into a higher harmonic wave. The fiber absorbs a part of an output of the fundamental wave or the pumping light, and heats the second fiber grating. The temperature of the second fiber grating is adjusted in accordance with an output of the higher harmonic wave outputted from the wavelength conversion element.