PURPOSE: To apply the self-steering function to two rear shafts by constituting the rear shaft fitting side of a torque rod lower than the trunnion shaft fitting side in a two-rear shaft trunnion-type suspension device with a lower torque rod.

CONSTITUTION: When a car is turned to the left, for example, it is tilted to the right side of the proceeding direction. Thereby, a large downward force FD is applied to the right side trunnion shaft 3, it pushes down the fitting joint 2a section of the right side lower torque rod 2, swings the torque rod 2 by an angle Δα, then increases the distance CR between the fitting joints 2b of the first and second shafts 4, 5. On the other hand, a push-up force is applied to the left side, thus decreasing the distance between fitting joints 2b, 2d. Thereby, the self- steering function is generated in two rear shafts 4, 5. At this time, the displacement of two rear shafts 4, 5 is absorbed by the rubber R and smooth self-steering can be performed.