A polarization optical system includes a first polarization plate, arranged at the light incident side of a liquid-crystal light valve, for transmitting first polarized light (s-polarized light) included in light incident on the liquid-crystal light valve from an illumination optical system and a second polarization plate, arranged at the light exit side of the liquid-crystal light valve, for transmitting second polarized light (p-polarized light), different from the first polarized light (s-polarized light), included in imaging light emitted from the liquid-crystal light valve to a projection optical system, in which the second polarization plate is configured in such a way that its light-incident face is concave toward the liquid-crystal light valve.