An illumination device includes: an excitation light source that emits excitation light having a first wavelength; a fluorescent substance that, when irradiated with the excitation light, emits light having a second wavelength longer than the first wavelength and transmits a part of the excitation light, and thereby multiplexes and emits the transmitted excitation light having the first wavelength and the emitted excitation light having the second wavelength; and a driving unit that moves an irradiation position of the excitation light in the fluorescent substance with the passage of time.