A wavelength converter of the present invention is provided with a laser resonator including a fiber containing an laser-active material and a fiber grating formed in the fiber, a laser light source for emitting an excitation light to the fiber, and a wavelength conversion element for converting a fundamental wave of a laser beam emitted from the laser resonator into a harmonic, wherein the fiber is coiled and has the outer side thereof coated with a heat radiating member having a reflection surface for reflecting light having a wavelength of an excitation light. The wavelength converter is designed to prevent an efficiency reduction caused by the heat generation of a rare-earth doped fiber in a wavelength converter.