A varifocal optical device is provided. The varifocal optical device includes an optical lens, an actuator unit connected with the optical lens and having two areas that are bending-deformed in opposite directions to each other when a voltage is applied thereto, and a supporting unit to support the actuator unit, so that a focus of the optical lens is varied by the bending deformation when the voltage is applied to the actuator unit. Thereby, a driving displacement of the varifocal optical lens can be maximized.