1. A liquid crystal lens, comprising: a first substrate having a first electrode; a second substrate which faces the first electrode of the first substrate in parallel; a second electrode arranged outside the second substrate, the outside being an opposite side of the first substrate, and the second electrode having a hole; a liquid crystal layer provided between the first substrate and the second substrate and constituted by oriented liquid crystal molecules; an insulating layer attached to the second electrode and an inside area of the hole on the second substrate; a third electrode, which is transparent, being arranged and in contact with the insulating layer and covering the hole; a first voltage-applying unit configured to apply a first voltage between the first electrode and the second electrode to control an orientation of the liquid crystal molecules; and a second voltage-applying unit configured to apply a second voltage between the first electrode and the third electrode to control the orientation of the liquid crystal molecules, the second voltage being independent of the first voltage, wherein the first and second substrates and the liquid crystal layer have parallel and planar structures, the second substrate does not include a hole, the first and second substrates and the third electrode are not deformed even when the focus is to be changed, an opening portion of the liquid crystal lens corresponds to the hole, and the first voltage has a fixed value that imparts optimal first-stage optical properties to the liquid crystal lens by influencing the liquid crystal layer, and the second voltage is changed to vary second-stage optical properties of the liquid crystal lens by influencing the same liquid crystal layer.