To provide a polymer actuator capable of effectively converting the contraction force in the axial direction of a conductive polymer material caused through energization into the high contraction force in the radial direction.

A tightening collar 42 is disposed on the outer circumference of an arm part 12 of a stabilizer 11 of a suspension device of an automobile, and a friction member 43 fixed to an inner circumferential surface thereof faces the outer circumferential surface of the arm part 12. The outer circumference of the tightening collar 42 is covered by a conductive polymer net 44 formed by weaving thread-like conductive polymer material to be elongated/contracted by applying the voltage thereto in a cylindrical shape, the tightening collar 42 is contracted by contracting the conductive polymer net 44 by the energization to the conductive polymer material in the radial direction, and the friction member 43 is brought into contact with the arm part 12 to suppress the rotation. By converting the contraction force in the axial direction of each conductive polymer material into the high contraction force in the radial direction by the conductive polymer net 44, the tightening collar 42 is tightened and firmly contracted in the radial direction.