A projection image display apparatus includes: light source; polarization/separation element having a polarization/separation plane through which one polarized light passes and which reflects the other orthogonal to the one; an image display element for modulating the incident light into image light and reflecting the image light; and a retardation plate disposed between the polarization/separation element and the image display element: the retardation plate has refractive indices different between two orthogonal directions in an optical surface thereof, and gives phase difference larger than λ/4 to polarized light entering the optical surface and having a wavelength λ; and supposing z axis be a normal to a light entering/exiting surface of the polarization/separation element, y axis be perpendicular to z axis and a normal to the polarization/separation plane, and x axis be perpendicular to z- and y-axes, the first retardation plate has optic axis within xz plane and tilted to x axis.