A light source unit includes a first light source for emitting light in a first wavelength range, a luminescent wheel including a second light source for emitting light in a second wavelength range and a third light source for emitting light in a third wavelength range whose wavelength differs from that of the light in the second wavelength range, which are disposed circumferentially end to end in an adjacent fashion, a fourth light source for emitting light in a fourth wavelength range similar in color system to the light in the second or third wavelength range, and a control unit for controlling the fourth light source and the luminescent wheel to illuminate the fourth light source during a first color mixing period when a boundary between the second and third light sources is situated on an optical path of the light in the first wavelength range.