An optical element and a projection image display apparatus capable of obtaining excellent tolerance to light of high luminance and high output. The optical element includes a substrate transparent to light in a used wavelength band, and a birefringent layer including an obliquely deposited film containing hafnium oxide as a main component. The projection image display apparatus includes a liquid crystal display device having the optical element, a light source for emitting light, and a projection optical system for projecting modulated light, and the liquid crystal display device is disposed in an optical path between the light source and the projection optical system.