A diffractive optical element exerts a diffractive action on a display light that is emitted from a display unit. A folding mirror is provided on the opposite side of the diffractive optical element from the display unit to reflect the display light. The diffractive optical element includes a transmissive action part and a diffractive and reflective action part. The transmissive action part exerts a transmissive action to transmit therethrough the display light, which is incident from the display unit and is in a first polarization state, toward the folding mirror. The diffractive and reflective action part exerts a diffractive and reflective action to diffract and reflect the display light, which is reflected by the folding mirror and is in a second polarization state opposite to the first polarization state, toward the projection portion on an optical path.