An optical shifter includes at least one shifting section that periodically displaces the optical axis of incoming linearly polarized light. The shifting section includes first and second liquid crystal cells and a birefringent element. Each of the liquid crystal cells changes the polarization direction of the incoming light from a first direction into a second direction, or vice versa, responsive to a voltage being applied to the cell. The first and second directions are perpendicular to each other. The birefringent element changes its refractive indices with the polarization direction of the light incident thereon. The first and second cells and the birefringent element are arranged to transmit the incoming light in this order. The liquid crystal layer of the second cell compensates for a disturbance in polarization that was caused while the incoming linearly polarized light was transmitted through the liquid crystal layer of the first cell.