In an optical device, when viewed from a first direction, first, second, third, and fourth movable comb electrodes are respectively disposed between a first support portion and a first end of a movable unit, between a second support portion and a second end of the movable unit, between a third support portion and the first end, and between a fourth support portion and the second end of the movable unit. The first and second support portions respectively include first and second rib portions formed so that the thickness of each of the first and second support portions becomes greater than the thickness of the first torsion bar. The third and fourth support portions respectively include third and fourth rib portions formed so that the thickness of each of the third and fourth support portions becomes greater than the thickness of the second torsion bar.