To provide a liquid crystal optical element in which the temperature of a liquid crystal layer inside the liquid crystal optical element can be correctly measured and which is capable of size reduction.

A liquid crystal optical element includes: a first substrate provided with a common electrode; a second substrate provided with plural segment electrodes; a liquid crystal layer sealed between the first substrate and the second substrate via a sealing material; and temperature detection means disposed at a location between the first substrate and the second substrate at which the means can be in contact with a liquid crystal layer, for detecting the temperature of the liquid crystal layer.