An optical deflector comprising: a mirror; a frame (4, 4') surrounding said mirror; first and second torsion bars (2a, 2b, 2'a, 2'b) oppositely arranged along a first axis of said frame (4, 4'), each of said first and second torsion bars (2a, 2b, 2'a, 2'b) having an end coupled to a circumference of said mirror; first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) opposite to each other with respect to said mirror, for rocking said mirror around said first axis, each of said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) being coupled to both of said first and second torsion bars (2a, 2b, 2'a, 2'b); first and second coupling bars (5-1, 5-2) each coupled between said frame (4, 4') and one of said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) and arranged along a second axis perpendicular to said first axis; and a control unit adapted to control said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2), each of said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) being divided into first, second and third areas (G1, G2) from said first torsion bar (2a, 2'a) to said second torsion bar (2b, 2'b) in accordance with boundaries arranged along a first radial direction along a +30° to +60°-angled direction, a second radial direction along a +120° to +150°-angled direction, a third radial direction along a +210° to 240°-angled direction, and a fourth radial direction along a +300° to +330°-angled direction with respect to said first axis, the second area of said first semi-circular piezoelectric actuator (3'-1, 3"-1) being between said first and second radial directions, the second area of said second semi-circular piezoelectric actuator (3'-2, 3"-2) being between said third and fourth radial directions, first piezoelectric portions (3'-11, 3'-13, 3'-22, 3"-11, 3"-13, 3"-22) being formed in the first and third areas of said first semi-circular piezoelectric actuator (3'-1, 3"-1) and the second area of said second semi-circular piezoelectric actuator (3'-2, 3"-2), second piezoelectric portions (3'-21, 3'-23, 3'-12, 3"-21, 3"-23, 3"-12) being formed in the first and third areas of said second semi-circular piezoelectric actuator (3'-2, 3"-2) and the second area of said first semi-circular piezoelectric actuator (3'-1, 3"-1), said control unit being adapted to apply a first drive voltage (V Y1) to said first piezoelectric portions (3'-11, 3'-13, 3'-22, 3"-11, 3"-13, 3"-22) and a second drive voltage (V Y2) opposite in phase to said first drive voltage (V Y1) to said second piezoelectric portions (3'-21, 3'-23, 3'-12, 3"-21, 3"-23, 3"-12). a mirror; a frame (4, 4') surrounding said mirror; first and second torsion bars (2a, 2b, 2'a, 2'b) oppositely arranged along a first axis of said frame (4, 4'), each of said first and second torsion bars (2a, 2b, 2'a, 2'b) having an end coupled to a circumference of said mirror; first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) opposite to each other with respect to said mirror, for rocking said mirror around said first axis, each of said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) being coupled to both of said first and second torsion bars (2a, 2b, 2'a, 2'b); first and second coupling bars (5-1, 5-2) each coupled between said frame (4, 4') and one of said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) and arranged along a second axis perpendicular to said first axis; and a control unit adapted to control said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2), each of said first and second semi-circular piezoelectric actuators (3'-1, 3'-2, 3"-1, 3"-2) being divided into first, second and third areas (G1, G2) from said first torsion bar (2a, 2'a) to said second torsion bar (2b, 2'b) in accordance with boundaries arranged along a first radial direction along a +30° to +60°-angled direction, a second radial direction along a +120° to +150°-angled direction, a third radial direction along a +210° to 240°-angled direction, and a fourth radial direction along a +300° to +330°-angled direction with respect to said first axis, the second area of said first semi-circular piezoelectric actuator (3'-1, 3"-1) being between said first and second radial directions, the second area of said second semi-circular piezoelectric actuator (3'-2, 3"-2) being between said third and fourth radial directions, first piezoelectric portions (3'-11, 3'-13, 3'-22, 3"-11, 3"-13, 3"-22) being formed in the first and third areas of said first semi-circular piezoelectric actuator (3'-1, 3"-1) and the second area of said second semi-circular piezoelectric actuator (3'-2, 3"-2), second piezoelectric portions (3'-21, 3'-23, 3'-12, 3"-21, 3"-23, 3"-12) being formed in the first and third areas of said second semi-circular piezoelectric actuator (3'-2, 3"-2) and the second area of said first semi-circular piezoelectric actuator (3'-1, 3"-1), said control unit being adapted to apply a first drive voltage (V Y1) to said first piezoelectric portions (3'-11, 3'-13, 3'-22, 3"-11, 3"-13, 3"-22) and a second drive voltage (V Y2) opposite in phase to said first drive voltage (V Y1) to said second piezoelectric portions (3'-21, 3'-23, 3'-12, 3"-21, 3"-23, 3"-12).