A light source optical system (102, 103) comprising: an optical element having a reflecting surface to reflect first colored light emitted from an excitation light source; and a wavelength conversion unit configured to emit the first colored light reflected by the optical element, the wavelength conversion unit including a waveform conversion member (26D2) configured to convert at least a portion of the first colored light reflected by the optical element and incident on the wavelength conversion unit, into second colored light having a wavelength different from a wavelength of the first colored light and emit the second colored light, wherein a point P does not intersect with a light flux Q where the point P is a center of the first colored light on the reflecting surface of the optical element and the light flux Q is a light flux of the first colored light emitted from the wavelength conversion unit, further comprising: a light mixing device configured to mix at least one of the first colored light and the second colored light emitted from the wavelength conversion unit; and a light guide configured to guide the at least one of the first colored light and the second colored light emitted from the wavelength conversion unit to the light mixing device, further comprising a refractive optical element configured to guide at least one of the first colored light and the second colored light emitted from the wavelength conversion unit to an incident aperture of the light mixing element, characterised in that a plane including a straight line and another straight line is substantially parallel to a short side of the incident aperture of the rod integrator, said straight line including the point P and said another straight line being a straight line connecting a center of a projection image of the first colored light on the incident aperture of the rod integrator and a point R that is a center of a projection image of the first colored light on the wavelength conversion unit. an optical element having a reflecting surface to reflect first colored light emitted from an excitation light source; and a wavelength conversion unit configured to emit the first colored light reflected by the optical element, the wavelength conversion unit including a waveform conversion member (26D2) configured to convert at least a portion of the first colored light reflected by the optical element and incident on the wavelength conversion unit, into second colored light having a wavelength different from a wavelength of the first colored light and emit the second colored light, wherein a point P does not intersect with a light flux Q where the point P is a center of the first colored light on the reflecting surface of the optical element and the light flux Q is a light flux of the first colored light emitted from the wavelength conversion unit, further comprising: a light mixing device configured to mix at least one of the first colored light and the second colored light emitted from the wavelength conversion unit; and a light guide configured to guide the at least one of the first colored light and the second colored light emitted from the wavelength conversion unit to the light mixing device, further comprising a refractive optical element configured to guide at least one of the first colored light and the second colored light emitted from the wavelength conversion unit to an incident aperture of the light mixing element, characterised in that a plane including a straight line and another straight line is substantially parallel to a short side of the incident aperture of the rod integrator, said straight line including the point P and said another straight line being a straight line connecting a center of a projection image of the first colored light on the incident aperture of the rod integrator and a point R that is a center of a projection image of the first colored light on the wavelength conversion unit. a light mixing device configured to mix at least one of the first colored light and the second colored light emitted from the wavelength conversion unit; and a light guide configured to guide the at least one of the first colored light and the second colored light emitted from the wavelength conversion unit to the light mixing device, further comprising a refractive optical element configured to guide at least one of the first colored light and the second colored light emitted from the wavelength conversion unit to an incident aperture of the light mixing element, characterised in that a plane including a straight line and another straight line is substantially parallel to a short side of the incident aperture of the rod integrator, said straight line including the point P and said another straight line being a straight line connecting a center of a projection image of the first colored light on the incident aperture of the rod integrator and a point R that is a center of a projection image of the first colored light on the wavelength conversion unit.