To provide a light source device and a projection display apparatus which can display high-quality image even if part of a fluorescent material provided in a fluorescent wheel has such a defective region that affects image display quality.

The light source device includes: an excitation light source 9 configured to emit and stop excitation light at predetermined timing; the fluorescent wheel 4 to rotate the fluorescent wheel including the fluorescent material applied thereon for emitting fluorescent light in a predetermined wavelength range when irradiated with the excitation light; and an irradiation spot changing unit 1 to change a spot on the fluorescent material irradiated with the excitation light.