An illumination optical system (10, 40) comprising: a light source (11, 41) emitting light of a first wavelength; a fluorophore unit including a reflection region reflecting light of said first wavelength and a fluorophore region including a fluorophore emitting fluorescent light of a wavelength that differs from said first wavelength by the irradiation of light of said first wavelength, said fluorophore unit being capable of movement such that light from said light source is successively irradiated on said fluorophore region and said reflection region; an optical element (13, 43) separating light of said first wavelength into a first linearly polarized light component and a second linearly polarized light component, the second linearly polarized light being orthogonal to said first linearly polarized light component, the optical element guiding said first linearly polarized light component emitted from said light source to said fluorophore unit, the optical element being again irradiated by light reflected on said reflection region and by light emitted from said fluorophore region; a quarter-wave plate provided on the light path between said optical element (13, 43) and said fluorophore unit, wherein said optical element (13, 43) emits light of said first wavelength that was reflected by said reflection region and said fluorescent light that was emitted by said fluorophore region in the same direction, and said optical element (13, 43) reflects said first linearly polarized light component of light of said first wavelength and transmits said fluorescent light and said second linearly polarized light component of light of said first wavelength. a light source (11, 41) emitting light of a first wavelength; a fluorophore unit including a reflection region reflecting light of said first wavelength and a fluorophore region including a fluorophore emitting fluorescent light of a wavelength that differs from said first wavelength by the irradiation of light of said first wavelength, said fluorophore unit being capable of movement such that light from said light source is successively irradiated on said fluorophore region and said reflection region; an optical element (13, 43) separating light of said first wavelength into a first linearly polarized light component and a second linearly polarized light component, the second linearly polarized light being orthogonal to said first linearly polarized light component, the optical element guiding said first linearly polarized light component emitted from said light source to said fluorophore unit, the optical element being again irradiated by light reflected on said reflection region and by light emitted from said fluorophore region; a quarter-wave plate provided on the light path between said optical element (13, 43) and said fluorophore unit, wherein said optical element (13, 43) emits light of said first wavelength that was reflected by said reflection region and said fluorescent light that was emitted by said fluorophore region in the same direction, and said optical element (13, 43) reflects said first linearly polarized light component of light of said first wavelength and transmits said fluorescent light and said second linearly polarized light component of light of said first wavelength.