A liquid crystal optical device of an embodiment includes: a first substrate unit; a second substrate unit; and a liquid crystal layer interposed between the first substrate unit and the second substrate unit. The liquid crystal molecules on a side of a first alignment layer of the first substrate unit is aligned perpendicularly to a first principal surface of the first substrate unit while the liquid crystal molecules on a side of a second alignment layer of the second substrate unit are aligned horizontally along a second direction. The opposing electrode includes: a first region and a second region, the first region has N first openings, and the second region includes M second openings, N being an integer of 0 or greater, M being an integer of 1 or greater, M being greater than N.