An illumination device includes a housing including an opening portion, a wavelength converting component which is disposed inside the housing and radiates wavelength-converted light having a different wavelength from that of a laser beam after the laser beam enters the component, an optical film which covers the opening portion and has optical properties such that the transmittance for the wavelength-converted light is 80% or more and the transmittance for the laser beam at the peak wavelength is 80% or less of the transmittance for the wavelength-converted light at the peak wavelength, and a light diffusing structure which is disposed on at least part of the inner wall of the housing and diffusely reflects the laser beam reflected at least by the optical film.