To provide a method for manufacturing a polarized light hologram element including a proton exchange layer which reduces lateral broadening.

The method for manufacturing a polarized light hologram element comprises the steps of; forming a metal layer mask 5 on a substrate 2; subsequently immersing it in a liquid for a proton exchange treatment and applying an external electric field in the direction of thickness of the substrate 2 to form a proton exchange layer 3; furthermore etching it for a specified time period using a selective etching solution which etches the proton exchange layer 3 and the metal layer mask 5 but does not etch the substrate 2, and; removing the metal layer mask 5 with etching and forming grooves on the proton exchange layer 3.