The present invention provides an optical element, optical unit, and image-taking apparatus which can reduce heat generation in the optical element and accurately control a refractive index profile of the optical element. The optical element has a liquid crystal layer composed of transparent liquid crystal molecules; a first electrode placed along the liquid crystal layer; multiple transparent second electrodes placed along the liquid crystal layer on the opposite side of the liquid crystal layer from the first electrode, with a voltage being applied between the first electrode and each of the multiple transparent second electrodes; and multiple transparent transistors placed along the liquid crystal layer together with the multiple second electrodes to adjust the voltages applied to the multiple second electrodes.