A projection-type image display apparatus including: a light source unit; an optical modulator including an incident surface and an output surface both being perpendicular to an optical axis of a light beam emitted from the light source, and configured to modulate a light beam emitted from the light source; a first polarizer provided to a surface of the optical modulator; and a second polarizer provided to another surface of the optical modulator. In the projection-type image display apparatus, the polarization direction of a light beam allowed to pass through the first polarizer and the polarization direction of a light beam allowed to pass through the second polarizer are substantially orthogonal to each other, and the light source unit emits a cross shaped light beam.