A projection display apparatus includes a polarization beam splitter, a light source, a polarization changing device, an optical uniformizing element, a light valve module and a projection lens. The light source emits an illumination beam. The polarization beam splitter, the polarization changing device, the optical uniformizing element, and the light valve module are disposed in the optical path of the illumination beam. The polarization beam splitter transmits the illumination beam. The polarization changing device changes the polarization direction of the illumination beam and reflects the illumination beam back to the polarization beam splitter. The optical uniformizing element is between the polarization beam splitter and the polarization changing device for uniformizing the illumination beam. The light valve module converts the illumination beam reflected by the polarization changing device via the polarization beam splitter into an image beam. The projection lens is disposed in the optical path of the image beam.