A projection display apparatus includes: a micromirror device that reflects light on an image display surface to emit image light; a prism unit that bends an optical path of the image light emitted from the micromirror device; and a projection optical system that includes a diaphragm and that projects the image light emitted from the prism unit onto a screen, wherein the image display surface is formed with a plurality of micromirrors, and an image is formed on the image display surface through ON/OFF control on a tilt of a surface of each of the micromirrors and intensity modulation on incident light, the prism unit has an air gap tilted at a predetermined angle with respect to a principal ray of the image light emitted from the center of the image display surface, and the image light emitted from the micromirror device passes through the air gap.