To provide a mask for manufacturing an alignment layer, with which an alignment treatment can be carried out in an easy and simple method and workload of a worker required for an alignment work can be reduced.

The mask 60 for manufacturing an alignment layer is to be used in a process of irradiating an alignment layer material 18d with linearly polarized light, and is equipped with: a translucent base 61 that transmits light; a polarizing layer 62 disposed on the translucent base 61 and comprising a plurality of metal thin lines alternately arranged in stripes at a period shorter than the wavelength of light; and an alignment mark A2 disposed on the translucent base 61 and formed of the same metal material as the polarizing layer 62.