Disclosed are patterned light irradiation apparatus, three-dimensional shape measuring apparatus, and patterned light irradiation method. The pattern light irradiation device for irradiating light having a pattern to a physical object, includes a pattern forming plate provided with a plurality of opening portions; a light irradiation unit for irradiating light to the pattern forming plate; and a projection lens irradiated by the light irradiation unit, for integrally condensing light passed through an opening of the pattern forming plate and guiding the condensed light to the physical object,wherein the projection lens is arranged such that an image of the pattern forming plate is not focused onto the physical object, but is projected as a sinusoidal wave pattern.