A projection display device includes an imaging element, a light source, a light valve that modulates light from the light source and emits modulated light in a prescribed polarization state, and an imaging optical system. The imaging optical system includes a first optical system that is used in common in projection and imaging, a second optical system that is used only in projection, a third optical system that is used only in imaging, and a separation member that separates an optical path from the second optical system toward the first optical system from an optical path from the first optical system toward the third optical system. The first optical system comprises a quarter wave plate and a polarizer arranged in a state of transmitting the light emitted from the light valve.