the distances r 12 and r 22 remain smaller than the distances r 11 and r 21 when the micro mirror 51 is in a horizontal state on the other hand when voltages v 11 v 21 and v 4 applied to the first and second address electrodes 31 and 35 and the micro mirror 51 have the relationship v 11 lt v 21 lt v 4 the electrostatic force f 11 acting between the first address electrode 31 and the micro mirror 51 is greater than the electrostatic force f 21 acting between the second address electrode 35 and the micro mirror 51 as shown in fig7 accordingly the micro mirror 51 rotates toward the first address electrode 31 side of the substrate 21 and is inclined to a position where the electrostatic force f 11 is balanced by the sum of the electrostatic force f 21 and the restoring force of the hinge or post such that the condition of r 11 lt r 21 is satisfied here voltages v 12 and v 22 are applied to the first and second auxiliary electrodes 41 and 45 and voltage v 4 is applied to the micro mirror 51 so.