A phase modulation device of the present disclosure includes: a light source; and an optical phase modulation element including a plurality of pixels in each of which liquid crystal molecules are arrayed, and including a plurality of pixel regions each including the plurality of pixels, the optical phase modulation element modulating, for each of the pixels, a phase of incident light entering the plurality of pixel regions from the light source. The optical phase modulation element includes, as the plurality of pixel regions, at least one first alignment region where an alignment direction of the liquid crystal molecules is a first direction parallel with a polarization axis of the incident light, and at least one second alignment region where an alignment direction of the liquid crystal molecules is a second direction parallel with the polarization axis of the incident light and different from the first direction by 180 degrees.