An object is to provide an exposure method of a photoalignment layer in which an alignment pattern having no disorder can be formed.
The exposure method of a photoalignment layer includes an exposure step of disposing an exposure mask and a substrate that includes a coating film including a compound having a photo-aligned group such that the exposure mask and the coating film face each other, irradiating the exposure mask with light to which the compound is photosensitive, and exposing the coating film through the exposure mask, in which the exposure mask is a polarization diffraction element having an alignment pattern where an optical axis changes while continuously rotating in at least one in-plane direction, in an image obtained by observing a cross section taken in a thickness direction along the one in-plane direction with a scanning electron microscope, the exposure mask has a bright portion and a dark portion extending from one main surface to another main surface, and has a region where the dark portion is tilted with respect to a perpendicular direction of a main surface, and in the exposure step, the coating film is exposed to light diffracted by the exposure mask.