A light wavelength converter comprising a substrate that is made of a material attaining a non-linear effect; an optical waveguide that is formed within said substrate; a light source that irradiates said optical waveguide with a pair of lights having a fundamental waveguide, said pair of lights being propagated within said optical waveguide and intersecting each other within said optical waveguide to thereby generate a second harmonic light; and a light deflection means that changes the intersection angle between the pair of waveguiding lights based on an electric signal that is input into said light deflection means, whereby, the phase matching condition of a pair of incident laser beams can be readily satisfied and, even when the ambient temperature changes, the second harmonic light can be stably generated.