A polarization conversion element includes: a plurality of polarization separation layers and a plurality of reflective layers alternately disposed along a first direction; and a plurality of retardation layers. The plurality of polarization separation layers reflect first polarized light of incident light along the first direction and transmit second polarized light along a second direction orthogonal to the first direction. The plurality of reflective layers reflect, along the second direction, the first polarized light reflected by a corresponding polarization separation layer. The plurality of retardation layers are provided on an optical path of one polarized light of the first polarized light and the second polarized, and convert the one polarized light to the other polarized light. The direction of a slow axis of one and another retardation layers are line-symmetrical about an axis along a third direction orthogonal to the first and the second directions.