In a wavelength conversion element in which a periodic poled crystal that converts an input laser light into a laser light of a predetermined wavelength is provided on a thick-film resistance substrate including a heating unit, a heat spreader having a predetermined thermal conductivity, which equalizes a temperature distribution of the periodic poled crystal, is provided between the thick-film resistance substrate and the periodic poled crystal, and the thick-film resistance substrate and the heat spreader, and the heat spreader and the periodic poled crystal are adhered by an adhesive member having a predetermined thermal conductivity.