A driving method of an optical element which comprises a liquid crystal layer including a liquid crystal compound and switching between a first state where the orientation of the optical axis is in a vertically or horizontally oriented state and a second state having an optical axis orientation different from the first state, wherein the first state voltage V 1 and the second state voltage V 3 have a relationship of Equation 1 below, and wherein the method comprises: a step of applying the second state voltage V3 to the liquid crystal layer in the first state to switch to the second state, and a step of applying a medium voltage VM satisfying Equation 2 below before applying the second state voltage V 3: V 1 < V 3 VT ≤ VM < VB wherein, V 1 is the first state voltage, V 3 is the second state voltage, VT is a critical voltage, VB is a back-flow voltage, and VM is the medium voltage, wherein the critical voltage VT is a minimum voltage at which fluctuation of transmittance occurs according to behavior of the liquid crystals responsive to an external signal, wherein the back-flow voltage VB satisfies Equation 5 below: VB = 0.3 × V 3 to 0.7 × V 3 wherein VB is the back-flow voltage and V 3 is the second state voltage, characterized in that the medium voltage VM is applied for a holding time TM satisfying Equation 7 below: 0.3 × T 12 ≤ TM ≤ 1.2 × T 12 wherein, TM is the medium voltage holding time, and T 12 is the time required for occurrence of 90% transmittance fluctuation in the response speed graph when voltage applied is changed from the critical voltage to the medium voltage. wherein the first state voltage V 1 and the second state voltage V 3 have a relationship of Equation 1 below, and wherein the method comprises: a step of applying the second state voltage V3 to the liquid crystal layer in the first state to switch to the second state, and a step of applying a medium voltage VM satisfying Equation 2 below before applying the second state voltage V 3: V 1 < V 3 VT ≤ VM < VB wherein, V 1 is the first state voltage, V 3 is the second state voltage, VT is a critical voltage, VB is a back-flow voltage, and VM is the medium voltage, wherein the critical voltage VT is a minimum voltage at which fluctuation of transmittance occurs according to behavior of the liquid crystals responsive to an external signal, wherein the back-flow voltage VB satisfies Equation 5 below: VB = 0.3 × V 3 to 0.7 × V 3 wherein VB is the back-flow voltage and V 3 is the second state voltage, characterized in that the medium voltage VM is applied for a holding time TM satisfying Equation 7 below: 0.3 × T 12 ≤ TM ≤ 1.2 × T 12 wherein, TM is the medium voltage holding time, and T 12 is the time required for occurrence of 90% transmittance fluctuation in the response speed graph when voltage applied is changed from the critical voltage to the medium voltage. a step of applying the second state voltage V3 to the liquid crystal layer in the first state to switch to the second state, and a step of applying a medium voltage VM satisfying Equation 2 below before applying the second state voltage V 3: V 1 < V 3 VT ≤ VM < VB wherein, V 1 is the first state voltage, V 3 is the second state voltage, VT is a critical voltage, VB is a back-flow voltage, and VM is the medium voltage, wherein the critical voltage VT is a minimum voltage at which fluctuation of transmittance occurs according to behavior of the liquid crystals responsive to an external signal, wherein the back-flow voltage VB satisfies Equation 5 below: VB = 0.3 × V 3 to 0.7 × V 3 wherein VB is the back-flow voltage and V 3 is the second state voltage, characterized in that the medium voltage VM is applied for a holding time TM satisfying Equation 7 below: 0.3 × T 12 ≤ TM ≤ 1.2 × T 12 wherein, TM is the medium voltage holding time, and T 12 is the time required for occurrence of 90% transmittance fluctuation in the response speed graph when voltage applied is changed from the critical voltage to the medium voltage.