To randomly set a value of a deflecting amount in the beginning of change of a spring rate of a stabilizer.

A structure with low torsional rigidity is used for one part of a straight portion in a stabilizer center. Its outer circumference is covered with a frame material, and one end of the frame material is fixed to the stabilizer. A contact surface A corresponding to a contact surface B provided on the stabilizer is provided inside the frame material. The contact surface A is directly attached to the frame material, or it is movable inside the frame material for changing a distance of the contact surfaces. During twisting of the stabilizer, the frame material and the stabilizer become a connected state by contact of the contact surfaces A and B, and the portion with low torsional rigidity of the stabilizer stops to function. Therefore the stabilizer becomes a state with high torsional rigidity, and the spring rate can be switched at a random deflecting amount. By this, the torsional rigidity can be conveniently adjusted from outside and the deflecting amount in the beginning of change of the spring rate can be randomly set without modifying a mounting part of the stabilizer to a car body.