An illumination device includes a light source configured to generate primary light having a Gaussian intensity distribution, an intensity-distribution converting member configured to convert the primary light to generate secondary light having a top-hat type intensity distribution, a wavelength converter configured to receive the secondary light from a light-receiving surface, generate tertiary light including the secondary light and wavelength-converted light in which a wavelength of the secondary light has been converted, and emit the tertiary light from an emission surface, and an antenna array having a plurality of optical antennas formed on the emission surface of the wavelength converter and arranged at a period larger than an optical wavelength of the secondary light in the wavelength converter.