This invention realizes an illumination optical system with a small etendue that has a longer lifetime and a high degree of brightness. The invention includes: a laser light source that generates excitation light having a first wavelength; a phosphor wheel including a blue fluorescent light generation region that generates fluorescent light having a second wavelength by means of the excitation light, and a green fluorescent light generation region that generates fluorescent light having a third wavelength by means of the excitation light; an LED light source that generates light having a fourth wavelength; and a dichroic mirror that reflects fluorescent light having the second wavelength and fluorescent light having the third wavelength and allows light having the fourth wavelength to pass therethrough, to thereby emit each of the lights in the same direction.