A variable stiffness stabilizer device (1) has a stabilizer bar (2) and actuators (3). The stabilizer bar (2) has a torsion bar (4) extending in the lateral direction (X1) of a vehicle and arms (6) connected through bend portions (5) to the ends (4a, 4b) of the torsion bar (4) and bendingly deformed according to the strokes of wheel supporting members (11). Variable bending stiffness parts (13; 130) of the arms (6) are rotatable about the axes (C1) of the arms (6), so that the bending stiffness of the arms (6) can be changed according to their rotational positions. The actuators (3) rotationally drive the variable bending stiffness parts (13; 130) about the axes (C1) to adjust the rotational positions of the variable bending stiffness parts (13; 130).