A wavelength conversion device includes a substrate, a matrix supported by the substrate and containing inorganic material, a phosphor embedded in the matrix, and filler particles embedded in the matrix. A linear expansion coefficient of the filler particles is equal to or larger than 25 ppm/K and equal to or smaller than 790 ppm/K, and is larger than a linear expansion coefficient of the matrix. This wavelength conversion device suppresses warping of the substrate.